Guren Ichinose/Relationships

Guren Ichinose at an early age would form a close relationship with Mahiru Hīragi. At school he befriended Sayuri Hanayori along with Shigure Yukimi and Mito Jūjō with Norito Goshi as well. Also drawing close to Shinya Hīragi around this time, these people would heavily influence Guren's decision where world changing scenarios were possible. They would also become members of his squad in the Moon Demon Company. Acquainted with another Hīragi family member, Kureto Hīragi who would become the Lieutenant General of the Japanese Imperial Demon Army, Guren worked to undermine the social order that shaped his early years but also actively fight against the overriding vampire threat. To build the world of his vision Guren would secretly align with vampire nobles including the third progenitor and queen of Japan, Krul Tepes as well as seventh progenitor Ferid Bathory. In both cases the goal was to acquire seraph related experiments of the Hyakuya Sect which he gained in Yūichirō Hyakuya. Placing him under Shinoa Hīragi's supervision Guren would have other black demon weapon holders Yoichi Saotome and Shihō Kimizuki join her squad in addition to Mitsuba Sangū.

After commanding soldiers at the battles of Shinjuku where he fought Mikaela Hyakuya and battling vampire nobles in Nagoya in which he murdered his own troops and vampires alike, Guren's status as a Namanari became more widely know which affected his relations with others. While others were concerned he was being possessed by his cursed gear demon Mahiru-no-Yo, Guren would separate them both into Mahiru and Noya in a plan to betray everyone. He was ready to overcome second progenitor Saitō's deception before successfully sealing the first progenitor Shikama Doji. Saying that he was motivated to resurrect all of humanity Guren was willing to attack Yu and Mika. Guren interacts with various other characters throughout the Seraph of the End series, which affects himself and the story. This article details Guren's relationships with other characters.

Sakae Ichinose
Guren's father. He is considered to be a moderate by the Order of the Imperial Moon and a weakling by the Hīragi Clan. He and Guren meet briefly before the Hīragi Clan executes him. Guren loves him dearly and was devastated by his death.

Unknown Mother
She dies while Guren is very young. Little has been revealed about her, but Sakae often says Guren reminds him of her. He says she was very wilful.

Sayuri Hanayori
As a servant to Guren, Sayuri cares deeply for Guren's well-being. He originally thought of her as annoying when she attempted to stand out in his eyes when they were teenagers. She is willing to follow just about any order Guren gives her, like jokingly attacking Goshi under his command whenever he goofs off. It is revealed that she has an unrequited crush on him, however Guren turns her down after she accidentally shared her feelings when they were sixteen. Despite this, her crush is why Sayuri would prioritize her infatuation with Guren over anybody else, such as Goshi when he tries to ask her out for a date. Sayuri is usually worried about Guren's injuries and helplessly cries over them. Guren had curry prepared for him by Sayuri for dinner to win over Guren's heart. Sayuri would go so far as to disobey her master's order if necessary, showing just how much she truly cares about him. Sayuri have also been Guren's retainer since her early childhood days where his mental struggles are understood by her.

Within the class room, Guren ignores her concerns of using his cursed gear sword to test the students. Whilst he considers her apprehension at Yoichi attempting the cursed gear trial he largely disregards it. Back to back fighting invading vampires together at Shinjuku, Guren does listen to her plan for them to hold off hostiles whilst Guren goes for the commander. As a member of his squad Guren would free her from confinement after the massacre at Nagoya airport. As Guren was turning into a demon Sayuri saw Mahiru near him and the process was interfered with.

Mito Jūjō
Teenagers together in volume 6 of Guren's light novels Guren would maturely reject her expressed romance towards him. He did not want to hurt her feelings and preferred to be just friend as usual. Yet the both of them still consider each other as a very important companion for one another to protect. Mito had always thought of Guren as someone, who she is deeply indebted to when believing that he has actually saved her multiple times. When she is near the brink of being killed by the Hyakuya Sect and being saved by Guren, Mito had thought of him in her mind, a prince charming to the rescue. Even until now, she continues to have an infatuated crush on him, one that remained for over 8 years and left unrequited. Nevertheless, Mito would tries to get involved with Guren whenever she possibly can if he is feeling depressed during his father's funeral because he was the only one, who treats her as a normal girl unlike the strict policy within her family. Though their relationship was first met with hostility every now and then, Mito began to show sympathy towards Guren and his harsh treatment by the higher-ups, regretting the cold things she said to him in the past. Another example was shown when she grew increasingly worried about the struggle Guren is going through like the death of his father, continuing to warm herself up to him.

As a member of his squad Guren would fight with Mito at the invasion of Shinjuku. He would have her scout the Ebina rest stop for vampires as Moon Demon Company members amassed to target vampire nobles in Nagoya. As a squad they would assault nineteenth progenitor Mel Stefano and prevail.

Shigure Yukimi
She is a member of the prestigious Ichinose family. Shigure have been a member of Guren's squad since she was 16 back in high school prior to the apocalypse. She cares deeply about Guren's well-being and tends to dote him with extreme loyalty as his retainers. Although Shigure is a quiet type and does not speak often when around Guren he could count on her to follow orders such as monitoring Shinoa squad. Shigure would also sometimes praise her master's well thought-out plan right after he defeated the nineteenth progenitor, Mel Stefano. Shigure is keeping her feelings of love for Guren to herself as unrequited. She wants to be useful for her master and knows that strength alone is not enough to support him whenever he is in trouble. This also goes along the line of wanting to bear the burden and sharing his master's pain alongside him. Guren is the only one who can break the cold gaze from Shigure whenever the two are around each other and would also cry about his injuries besides Sayuri. Shigure is quite observant and keen about what turmoil Guren must be going through as she sees him struggling mentally. On the other hand, she is overly protective of Guren whenever someone tries to make fun of him and look down on him because of his family status.

Norito Goshi
A member of Guren's squad since he was 16 back in high school prior to the apocalypse. He enjoys making fun of Guren. He makes use of Goshi's illusion based cursed gear in combat and non-combative situations.

Shinya Hīragi
Although he was adopted into the prestigious Hīragi family, he is Guren's friend. He was first seen trying to target the vampires in Shinjuku without hurting Guren.

It was because of the risks involved that Shinya volunteers himself to join Guren without orders to help him in the attack on Nagoya to ambush vampire nobles. Shinya takes part with Guren and Mito in the practice fight against Shinoa squad. When making their way to rescue hostages kept outside Nagoya city hall, Guren is checked on by Shinya aware that he doesn’t do too well when many comrades are killed. Shinya expresses concern since Guren knows the reality of war when people are lost but he beats himself up over it.

The two of them lead the ambush against Crowley. However, with the vampire nobles strength their plan turns out horribly resulting in Guren being captured. Later on, Guren leaves Shinya in charge of bringing the rest of his troops to the rendezvous point at Nagoya airport. There, a possessed Guren meets Shinya. Shinya tries to get Guren back to his senses but then realizes that Mahiru has possessed him already. Three months later, Guren returns from the Sanguniem wishing to speak to Shinya.

In the end of volume 7 of Guren's light novels, after Mahiru kills Shinya and torturing him to death, Guren panicked slowly dying at Guren hand, proving that he cared for Shinya the most from his squad. After the rest of his squad died at the final confrontation between Mahiru, Guren was devastated by their death especially Shinya which forced him to do the Seraph of the End experiment to revive his friends but also triggered the apocalypse. To Guren, Shinya is his best friend figure. He cared for Shinya the most when he was resurrected.

With Shinya's death Guren saw that as his chance to die as well. "Shinya and I... We were supposed to die together! If we could just die without becoming demons... Without getting obsessed with our powers... That was how we were going to beat them! How we were going to win!"

- Plans to die and overcome their adversaries involved Shinya.

During the battle of Shibuya, in becoming a demon Guren used a power to flatten Shinya and his squad to the ground. Even though a demon, and having stabbed Shinya when he was prevented from leaving and using Chains to sap his strength, Guren could speak how he was acting to defend them before departing. When remembering how his friends perished, Guren recalls holding Shinya.

Kureto Hīragi
The current head of the Hīragi family and the leader of the JIDA. From high school, the moment he met Kureto, Guren immediately noted his incredible strength and took him seriously, holding hardly anything back, when he attacked him with the intent to kill. Although he lost, it was only because of a surprise attack and he impressed Kureto enough that he requested Guren to become his subordinate. At first, Guren remained on antagonistic terms with Kureto, showing little respect and outright opposition when he seemingly tortured Shinoa to the point where he unhesistantly attacked him for trying to break Shinoa's neck. However, he trusted him with the information of the Cursed Gear that Mahiru left behind and the task of subduing and killing him if impossible to do so. Although this wasn't such a bad decision, as Kureto did live up mostly to Guren's trust by saving him and then ensuring the survival of the Order of the Imperial Moon along with giving Guren a chance to save Sakae by stealing his helicopter, Guren was left outraged with Kureto's inability to make Sakae go free and only reluctantly obeyed him to save his father. However, after seeing Kureto sincerely reward him for his successes despite failing to catch Mahiru by effectively lifting any chances of the Imperial Moon Order's destruction and even opposing Sakae's execution along with giving him time to talk to his father one last time, Guren begrudgingly thanked him. In the present time, they have become considerably more cordial. Guren still openly professes his dislike of Kureto's sinister experiments, distasteful at one point by him cruelly trying to painfully turn a Vampire into a Demon, but hides it effectively, and can even casually talk about him seeking more hostages, although he still fondly reminisces of how he had clashed swords with Kureto and openly flaunts his slightly superior, but still better, skills, making it clear he will kill him if he tries anything. Kureto suspects Guren is a spy for the vampires or may lead a coup against the Hīragi family, but he also says he trusts Guren and sends Guren on an extremely dangerous mission to Nagoya. As a namanari, Guren joins Kureto in beginning the Seraph of the End experiment by killing of his troops and enemy vampires. Three months later, they both join forces in ambushing the Sanguniem. He later promises Kureto that he will save him from Shikama Dōji completely possessing him, though Shikama Dōji went after Shinoa and left Kureto's body in the end.

Tenri Hīragi
Leader of the Japanese Imperial Demon Army as well as the Hīragi family, he looks down on Guren, who is from a lower branch family. Guren resented Tenri greatly for how his father was treated and cruelly executed and after he ascended to the Head of the Ichinose Clan upon his father being executed. Upon finally meeting Tenri he exuded a large amount of anger and hatred, which Tenri mockingly scoffed at, and did not relent even as Tenri stepped on his head, his wrath in fact increasing by every second to the point where it took all he had to stop him from attacking Tenri. Years later, Guren remains on antagonistic terms with Tenri, openly calling him and the rest of the Hīragi the worst and dull, at which point Tenri responded by coldly threatening to beat him, and he even works with Kureto, who he doesn't like too, against Tenri and fully supports Kureto's desire to kill his father. Later on Kureto kills Tenri and become the leader of the JIDA as well as the current head of the Hīragi family.

Aoi Sangū
She is the personal assistant of Kureto Hīragi. She arrives with him to the airport and releases the chain on his orders, ultimately resulting in the many losses of lives for their blood to activate the Seraph of the End.

Seishirō Hīragi
A higher-ranking member of the JIDA, he calls Guren a loser and tells him to get lost.

Aiko Aihara
In Nagoya, Aiko sobs out to Guren about the deaths of their comrades and blames herself for it, however he tells her that their deaths are under his hands and not hers.

Guren tells her to stay behind and to inform the other squads, who would later arrive of where their locations would be and their next instructions. She tearfully accepts and in return the others with her are allowed to rest.

Shinoa Hīragi
She is Guren's subordinate, and he assigns her to be the surveillance officer to both Yu and Kimizuki. Shinoa and Guren have a close relationship, and he says he would even let her kill him. Her sister is the demon inside Guren's sword. After learning that Guren has been experimenting on Yu, she asks him what his real intentions are. She becomes more concerned after learning that her sister may be influencing Guren behind the scenes. However, she remains loyal to Guren. A member of the prestigious Hīragi family. She is shown shocked like all of her squad when he slaughters his fellow troops at Nagoya.

At Shinjuku Guren worked to suppress Shikama Dōji who was possessing Shinoa so that she could regain her own body.

Yūichirō Hyakuya
When Yu escapes Sanguinem, Guren takes him in and trains him as a soldier and secret weapon of the Japanese Imperial Demon Army. Guren knows he was a survivor of the Hyakuya Orphanage, and saves him with the first intention of experimenting on him. Though throughout their four years together, they develop a close relationship, and Guren acts as a father/mentor figure to Yu. Teaching him how to fight, Guren would repel Yu's attacks and kick him away, yet guided him to live, gain power, then get revenge. However, Guren will scold Yu when he doesn't follow his orders on battlefield, an example when he punched Yu for not activating the curse on Mikaela in Shinjuku.

Before the war, Guren tells Yu to not follow the Hīragi Family, as the one who saved Yu was him and that Guren "owns" him. Upon arriving late for Guren's speech, Guren used Yu as a hostage under Goshi's illusion spell as punishment for the Shinoa squad. During their match with the kids, Guren engages into one-on-one combat with Yu, defeats him and the Shinoa squad.

During the ambush against Crowley, Yu makes his all of his attempts to rescue Guren, but commands that they leave to the rendezvous point immediately. Upon retreating, Yu was then heartbroken that he failed to save Guren. In a flashback, Guren was shown trying to comfort Yu from a nightmare. This resulted to Yu overdosing the pills which was then followed by his death. He later on wakes up with Asuramaru's power to rescue Guren once more from Crowley. When Yu turns into a half-demon, Guren tells him to get back to his senses.

Later on, a possessed Guren meets up with Yu once more with a grim greeting. Yu tried to get Guren back to his senses and this gave Guren a little moment of his humanity. However, the demon's influence took over Guren and he mercilessly stabs Yu. It is revealed to Kureto that he found Yu through Mahiru connections with Saitō who was working at the Hyakuya Sect.

Finding Yu again Guren states he requires him as a part of his plan to resurrect humanity. After freeing Yu from his confines at Shibuya Guren waited for Mika to join them before attacking them both. He meant for Yu to claim Mika as a demon to be bound to cursed gear in a bid to undermine the first.

"Exactly. Don't forget that you count as part of the family too."

- Knowing that mentioning family will always resonate in Yu.

One more than one occasion Guren has used the notion that they are family to induce Yu into co-operating with him. With Yu's impression of him to begin with Guren can persuade Yu that Mika being turned into cursed gear is a way to help him and Shinoa.

In a quest to betray everyone, and in becoming a demon, Guren focuses on attacking Yu. With his goal complete of having Mika turn into a demon, Guren means to have Yu get him as his cursed gear. Answering Yu's questions, Guren answers yes he does like Yu, and is also using him. When hesitating when responding to whether he was involved with Ferid murdering Yu's family, Guren attempts to say he can explain. After their clash, Guren notes how Yu has become stronger.

"Hah! Look at that idiot. After all that, he's smiling. He's gotten stronger."

- Regarding Yu who he was attacked by.

Where Guren had always won in previous battles, he calls for Yu to not go getting cocky as he resumes fighting. Believing himself to be victorious, Guren's attitude to Yu's grief over his family is to regard their fight as a friendly training one.

"That was fast, Yu. But looks like today's another victory for..."

- Bearing over him, Guren views his battle with Yu as a friendly sparring match, indifferent to his grief that his family was murdered.

Taking to kneeing Yu as he attempts to get him off him, Guren only changes his brutality after hearing that Yu needs to win so that Guren can depend on him. In response to Yu's honest feelings, Guren thinks he is weak before he forfeits the battle. Answering that Yu won, Guren then confirms that he murdered Yu's family.

"I did. I'm sorry."

- Confirming he murdered Yu's family.

Surprised to hear that Yu forgives him, Guren is upfront that he had them killed for selfish reasons. He does see Yu as the victim. Hearing Yu say he can depend on them, in being asked to join hands with him and the squad, visualisations of Guren's own squad are seen. Whatever the problem is, Guren is told they can solve it together, and he can even lie about his plan. From this scenario, Guren claims he will tell Yu the truth.

Shihō Kimizuki
A soldier Guren experimented on. Guren is aware that his sister, Mirai Kimizuki, is under hospital care but Guren was not certain Kimizuki was ready to acquire a black demon weapon although he would eventually. Having Kimizuki become a member of Shinoa's squad Guren would be on the same battlefield as him in Shinjuku. When Guren was a demon with the Hyakuya Sect attacking Shunjuku while Shikama Dōji was in it Guren murdered Mirai which greatly enraged Kimizuki. The rage had not subsided and Guren was attacked then next time they met however Guren's claims of being able to resurrect everyone quelled Kimizuki's anger.

Yoichi Saotome
He is a soldier Guren experimented on and collected after the Hyakuya's downfall. In addition, after he became Yu's first official friend having helped challenge a vampire, Guren arranges for Yoichi to wield a Black Demon. Guren told Yoichi to give up if he had any doubts about the ceremony, and told Yu and Kimizuki that Yoichi needed to be killed when the demon took over. Despite that Guren was the only one able to get through to Yoichi when he raised whether Yoichi wanted to remain under the bed and watch his sister die, or do something about it. He is a member of Shinoa's squad. He praised Yoichi for knocking Kimizuki out to stop him attacking Guren in his fury however when Yoichi learned that Guren had his sister, Tomoe's body Guren leapt away from Yoichi's attack. Finding him again with Yoichi aiming his bow at him Guren questioned what if it were the case that Tomoe's murder was a part of his plan.

Mitsuba Sangū
She is a soldier of the Moon Demon Company. Guren arranges for her to join under Shinoa as part of her squad and he asked her not to try anything when she charged towards Shinoa. Patting Mitsuba on the head, he wanted the squad to stick together without anyone going solo as Guren glanced at her. Guren calls to Mitsuba to help prepare a spell circle for containing a black demon.

Makoto Narumi
A member of his own squad. He suffers the loss of Yayoi and Taro when the vampires ambush them after Mikaela has taken away Yūichirō. Along with most others, he escapes and arrives at the airport. He prevents Rika from killing Shinoa out of anger and resent, but also turning on Shinya and proclaiming that he and a few others will head back to the town hall and rescue Guren. He has very great respect for Guren, wanting to be a great swordsman like him as he practiced daily.

When Kureto arrives, he's wary of the Lieutenant General and refuses to rest. Later on he openly confronts Kureto about his plans and everything he's suffered. When the chains are released, he witnesses the death of the rest of his squad. Before he could attack Kureto for revenge and be slain on the spot, he is helped by the Shinoa squad.

Shūsaku Iwasaki
A member of Makoto Narumi's squad. During the skirmish between Guren and Yu at Ebina rest stop, he noted that Yu's power alone was not enough to defeat the Lieutenant Colonel. Later, just like with Rika, he escapes the vampires' ambush and arrived at the Nagoya Airport. Soon after when Kureto arrived, he is brutally stabbed by several chains to help activate the Seraph of the End, dying soon afterwards after telling Makoto to run.

Masanori Hanayori
Sayuri's father and leader of her clan.

Mitsuki Iori
An occult researcher working in the mountains of Aichi Prefecture. Guren amputates her left hand when it becomes tainted with her blood and attempts to devour her.

Samidare Yukimi
Shigure's father and leader of her clan.

Mahiru Hīragi
Guren's lover and Shinya's former fiancée. They met when they were children and quickly fell for one another. Their violent separation made Guren want to gain more power to be able to be with her. However, when Mahiru tried to reconnect with him, Guren acted cold around her, even going as far as to congratulate her for being engaged to Shinya and later on praising his female retainers in her back as if to mock her, to great success, as he believed he was not strong enough yet. Despite this, it is demonstrated repeatedly that Guren still cares for her, as while exasperated by how much she had fallen, Guren never gave up hope that she could be redeemed and continued to try to reach out to her, especially her human side. Guren absolutely refused to kill her even when she herself begged him to do so. Instead they consummated their relationship, and even when his father was taken hostage Guren found it very hard to bring himself to kill her and even opted to kill both himself and her out of regret of being unable to fulfil his promise to save her. After Mahiru had ruthlessly massacred all his friends, Guren still wanted to save her where even though he had always chosen his friends over her, in the end Guren could never bring himself to truly hate her despite stating coldly he hates her after she killed Shinya. He was utterly devastated by her death at the hands of his former demon to the point he even questions why he was still alive and requested to be killed by Ferid but he told him to not give in, to despair. Despite her impressive genius, all she wants is to love Guren and she retains her love for him, be as twisted as it is, even as she steadily becomes darker. Inventor of the Cursed Gear, Mahiru eventually becomes consumed with her research and fuses with Noya to become the demon Mahiru-no-Yo.

Where their plan involved turning Mika into a demon and then cursed gear, Guren discusses with Mahiru on their scheme afterwards. Unsure whether Yu hearing Mika's voice is a trick from the First, they mention their plan years in the making could be unravelled.

Kuro Kuki
A young boy, and the last surviving member of the Kuki clan. He despises and loathes Guren for him being an Ichinose. Kuro challenges Guren to a fight in hopes to defeat an Ichinose. On the other hand Guren see's him as a nuisance, having dealt with these situations many times. Although Guren hides the fact from him, probably due to him being only a young boy. Guren acts as a loser in front of him despite Guren having the upper hand in their fight. When a trap was laid and it turned back against Kuro and his friends, he saves them. Guren berates him for being reckless and lectures him as his friends almost got killed. After that both of them come in good terms with each other and Kuro respects Guren.

Ferid Bathory
An extremely powerful vampire, he works with Mika. Ferid plays with Guren on the battlefield at Shinjuku, though it's revealed later that he and Guren had been working together for some time, which explains a lot of the supposed coincidences throughout the story. In the light novel volume 2 he comes across Guren and Mahiru in Ueno Zoo and he easily defeats both of them. He breaks Guren's left hand and many other bones but Guren survives it as Ferid wonders if he is a human or not. He meets Guren again in volume 7 while Guren was performing the Seraph of the End experiment to resurrect his friends however when Guren recognizes him from before and tells Ferid to kill him who is now his heart is empty and filled with despair but Ferid rejects that, telling him to not fall in despair and decide for himself thinking it's more amusing this way. He later helps him revive Shinya. In Seraph of the End: Guren Ichinose: Resurrection at Nineteen, He appears in Guren's apartment, Mahiru then forces Guren to kill him as she is the only one who should trust and not him. When Guren refuses so and explains to Ferid what happened to Mahiru and she's trying kill him. Mahiru then possess Guren and he fights Ferid. Ferid whom he came all this way just to die. After he fought with the possessed Guren, Mahiru informs him that he is in Shinjuku which death awaits him. However Ferid escapes informing Mahiru that it seems that he wants to die some other time.

Driven in a truck transported by Ferid, when asked if he was involved with the murder of the Hyakuya orphans, Guren answers Yu he needs to explain.

Saitō
A vampire disguised as a modified human working for the Hyakuya Sect. He does not reveal his real name on their first encounter. Saitō asks for Guren to join him multiple times, but Guren refuses to. He even reveals to Guren that he is a vampire that was a second progenitor. Saitō tells Guren that as long as he cares for his friends he can never catch up to Mahiru. Ferid reveals to Guren that Saitō was only using him all along.

Crowley Eusford
A thirteenth progenitor in Ferid Bathory's faction. He and his aides were the next targets under Guren's command. Upon seeing Guren during the ambush, Crowley makes a remark that his skills have gone better. Later on, he playfully chases after Guren and Shinya. As a result, he captures Guren.

Chess Belle
Her arrival along with Horn's makes it harder for Guren to be rescued during the Nagoya City hall operation. After being captured Guren is interrogated by her on how humans acquired so much power in so short a time.

Horn Skuld
With Chess and Crowley Guren would find this vampire noble at Shinjuku and then at Nagoya city halls. Captured, Guren would be pinned to the ground by her to prevent him interfering in Crowley and Yu's fight.

Mel Stefano
A nineteenth progenitor that Guren had difficulty fighting against, resulting in the losses of many lives while in the process of doing so though in the end Guren and his squad succeeded in defeating him.

Krul Tepes
Guren first met Krul once she arrived at Nagoya. Shortly after, Mahiru overtook his body and commanded Krul's assistance in an experiment at the airport. This told the ruler of Sanguinem that Guren and Mahiru, a woman she knew from eight years past, were connected.

Having sought out Krul, he travels with her as they progress with their plan.

Shahal
An anime-only vampire, who captures a girl named Riko. Guren orders Shinoa Squad to rescue Riko from him.

Mikaela Hyakuya
Coming across this powerful young vampire at Shinjuku Guren even with assistance from his squad is nearly killed by him. Guren calls him a naive brat but also a polite vampire. Hearing that Mika is Yu's best friend and adopted family member, and inferring that he may have the seraph gene as a survivor of the Hyakuya Orphanage, Guren agrees to help Yu get Mika back. Understanding that Mika may have reasons for wanting to kill him Guren largely disengages from any hostile courses of action by focusing on other matters when Mika is around. By attacking Yu and Mika at Shibuya Guren would be a major factor in Mika's sacrificial act which was part of Guren's plan to produce a black demon. Mika, along with Yu, is one of the important details for Guren to resurrect humanity.

Mahiru-no-Yo
Though while she might let Guren take the lead for the most part, she's not above possessing him to achieve her own ends, which she proves in Nagoya. Guren's relationship with Mahiru now is seemingly even more complicated than before, as he acts even colder whenever she asks him to obey her and shows such annoyance at her sarcasm to the point of being quick to exasperatedly demand her to shut up and even at times telling her to die but as revealed just before he started to become a demon, he had never forgotten that it was his inability to help her that she became a demon, expressing genuine remorse over his failure, and was encouraged or perhaps even touched by her adamant defence of him to begin the process. By throwing his sword into them Guren was able to separate Mahiru-no-Yo back into the component parts of Mahiru and Noya.

Noya
A demon prepared by Mahiru, whom Guren forms a contract with in book 4 of Catastrophe at Sixteen. When Mahiru stabbed herself using Noya and integrated with the demon into her heart, Noya was fused with Mahiru and became his current demon Mahiru-no-yo. It is later revealed that Noya was actually alive all along instead of completely vanished by the merging, but since he was inside Mahiru he managed to erupt from her body after Guren called his name. However Guren is aware of Noya unknown intentions, despite that he released him from his Cursed Gear to help him in the battle against Yu and Mika. Later Guren leaves Noya when Mahiru injects him with a needle, rendering him unconscious.

Asuramaru
The demon Yu creates a contract with. He has a connection to Guren, as he was Mahiru's previous demon. Mahiru leaves Asuramaru in his care, and he in turn gives Asuramaru to the Hīragis for research purposes. Guren knew that Yu's Cursed Gear is strong, and he told Shinoa to give him special pills different from his other squad members. Asuramaru on the other hand, doesn't trust Guren completely.

Demon Mika
Mika is reborn as a demon due to the fact that Guren injected him with a drug and later killed him. When the demon go out Mika's face, Guren immediately said that he was a demon of a black class. Guren sees nothing wrong with having a hand in Mika's murder, and then having him change into a demon to be bound to a weapon for Yu to use. Hearing that Yu heard Mika call to him Guren still acts as if though Mika is a memoryless demon who is to be bound. He also realizes that Mika is incredibly powerful as a demon and distinguishes from other demons, so he gives Yu advices on how to defeat him correctly.

"He'll be powerful. He's the first's son, after all. He's more powerful than any black demon. Give it your all."

- An unwavering view that Mika has become a demon without memories

Judging by Guren's words, his main goal is to connect Mika as a demon with Yu, so that Shikama does not find him, and then use him for his plans (killing Shikama and the resurrect of humanity).