A meddlesome vampire who is always smiling. He allows Yūichiro Hyakuya to escape in 2016 and fatally injures Mikaela Hyakuya. She believes he intentionally allowed Yu to escape. She punishes him for his actions but shows him mercy. Since then, he uses blackmail about her dabbling in the seraph of the end against her to prevent her from killing him. He is extremely fond of Mikaela and touches him at every opportunity, much to Mika's displeasure. He claims that Mika is his favorite servant while Krul states she is Mika's owner. He adores her angry expressions and claims to love her. Although she originally has a distaste for him, this distaste develops into a hatred over the next four years. She comes to want him dead. He eventually dethrones her in an ambush alongside Crowley but both are later sentenced to exposure torture.
A thirteenth progenitor and member of Ferid's faction. Currently residing in Nagoya. He attacks Krul Tepes on Ferid's orders to keep her distracted.
After the humans unleash the Apocalypse on Japan in Christmas of 2012, she invades Tokyo and collects him and the other Hyakuya Sect orphans. Instead of killing them, she disobeys her orders from the Progenitor Council and raises them in Sanguinem. He attempts to escape from Sanguinem with his family in 2016, but Ferid Bathory slaughters everyone but Yu and fatally wounds Mika. He rejects her offer of immortality, but she saves his life against his will and turns him into a vampire by kissing him. She shows him pity and allows him to drink her blood instead of human blood, but she appears to enjoy his dependence on her and claims he will be her dog for all of eternity. She treats him gently and is often shown hugging him. For the next four years, she teaches him how foul and nasty humans are, they come to a close relationship, she motivates Mika to rescue Yu from them and their experimentation.
In 2020, Mika works as a city guard with Lacus Welt and René Simm, and he is commonly known as her favorite pet. He is one of the seraph of the end. When he expresses concern that Krul only wants to use him and Yu like those humans, she calms him down by revealing her true plans. She sends Mika to find Yu.
When Krul and Mika tried to rescue Yu during the battle on Nagoya Airport, they were ambushed by Ferid and Crowley. Before getting captured, Krul orders Mika to leave and tells him an unheard order before falling unconscious.
Although he is younger than Krul by 200 years, he claims to be stronger than her. He wants to take her place as the ruler of Japan and recently wiped out some spellcasters in Europe. After he appears in Japan with Urd Geales, he meets Krul after Saito flees. Lest asks Krul what happened in Japan. Later watches as Urd sentences Ferid and Krul to exposure torture.
A fifteenth progenitor and a member of Lest Karr's faction. He resides in Nagoya. He is annoyed by Krul Tepes and her "insufferable attitude." He refuses to obey her orders and states that he is not her subject. When Esther informs him that Krul intends to visit Nagoya in person, he reconsiders disobeying her. He is killed by the Moon Demon Company.
Urd watches Ferid claim that Krul is a traitor to the Progenitor Council. He fights Saitō and catches Krul when Saitō flees. He carries her by her neck back to Osaka Bay and sentences her to exposure torture.
Krul meets Saitō when he appears at Ferid's mansion. She questions him about if he is working with Ferid but Saito claims he disposed of Ferid a long time ago. She remembers him as the one who tagged behind the First Progenitor and remembers when the first progenitor took Ashera Tepes and turned him into a demon. After his fight with Urd, he flings Krul and flees.
Krul dislikes and despises Sika, the first progenitor, for taking her brother from her and turning him into a demon. Saito notes that all vampires dislike him to some degree for turning them into undying bloodsucking monsters. He sired Krul and shown interest in her brother Ashera Tepes which he took away, begging him to bring back her brother and not go with him but Sika simply ignores the heartbroken Krul, and Ashera says this is for their future. Ever since it has been her goal to find her brother.
The human responsible for turning Yuichiro Hyakuya into a monster. Yu is a member of his Moon Demon Company. He was Mahiru's lover, and she now resides in his sword after Mahiru sacrificed herself. She states to him as Mahiru's messenger.
After the humans unleash the Apocalypse on Japan in Christmas of 2012, she invades Tokyo and collects him and the other Hyakuya Sect orphans. Instead of killing them, she disobeys her orders from the Progenitor Council and raises them in Sanguinem. He attempts to escape from Sanguinem with his family in 2016, but Ferid Bathory slaughters everyone but Yuichiro Hyakuya and fatally wounds Mika. Yuichiro flees to the surface, where the Japanese Imperial Demon Army picks him up and later begins experimenting on him as one of the seraph of the end.
Mika encounters him on the battlefield in Shinjuku in 2020, and Yuichiro transforms into an uncontrollable monster. He stabs Mika through the back and chest and harms him enough to make Mika require curse detoxification. Even so, Krul claims to like him. She supports Mika's familial love and sends him to rescue Yuichiro from the humans.
When she senses that her brother Ashera Tepes is Yu Cursed Gear, she then knew that Mahiru kept her part of their bargain.
At some point, in the Dark Ages of Greece, a young Yu come across her wanting to see the "Mikaela" she tells him to keep it a secret he agree's to but being ignorant as he is a young questioning the meaning behind it which puts Krul in a desperate situation.
Krul's long-lost brother. He was originally Ashera Tepes. They were both born in a family of nobility along with their mother. She and her brother were attacked by the rebels who hate nobles, then she and Ashera were separated. He became a demon after Sika Madu took him, now taking the name Asuramaru. Mahiru Hiragi stole him and used him as her black demon weapon in the Catastrophe light novels. In volume 5, Krul asks Mahiru about his whereabouts. She is unaware that Asuramaru now serves Yuichiro Hyakuya as his Cursed Gear. In Chapter 49 of the manga, it is revealed that Krul cares deeply for her brother as she cries and pleads him not to go.
Much later she is now aware that her brother resides in Yu Cursed Gear after sensing his presence. Krul is then determined to save him.
Before becoming a demon, she was Mahiru Hiragi. She is traitor of the Hiragi family who joined the Hyakuya Sect. She uses Asuramaru as her demon weapon. Mahiru predicts the end of the world and warns Krul about what is to come and tells Krul about the seraph. She eventually becomes a demon herself by sacrificing herself, Guren Ichinose and now exists as the demon Mahiru-no-yo bound within Guren's sword. Prior to Mahiru's death, Krul turned her into a vampire.
In the Dark Ages of Greece Noya was there with her. He didn't care much of Krul's concerns that they have been seen by Yu, having been convinced that their secret is still safe. Krul on the other hand disliked his actions. Noya attempts to ease her suffering and concerns. In the present time Krul is also concerned about his actions, since he is after her brother Ashera.
Krul has a largely unique relationship with Arukanu being one of the few vampires to keep animal like pets. She keeps Arukanu as a familiar of some sorts and for their part returns the affection with a strong amount of loyalty by sticking near her when present.