Raimeiki

"You always maintain impeccable self-discipline. And that's why you're so drawn to Guren. That's what made you so jealous of Mahiru. Both of them gave in to their desires so easily."

- Raimeiki's shadow to Kureto

Raimeiki (雷鳴鬼) is a high-ranked, possession-type demon of the Black Demon Series. She formed a contract with Kureto Hīragi and became his Cursed Gear.

Appearance
Raimeiki manifests as lightning surrounding the blade. Her true form is revealed to be that of a young woman with sharp slanted eyes, a black horn protruding from her forehead, and long unkempt hair that is held down by a black wide headband that sits behind her horn with some strands sticking out. As a former vampire, she has pointed ears and fangs, which adds to her wild looking appearance.

Her outfit is the most revealing of the demons so far with her top being covered by two black cloth strips that are wide in the middle to cover her breasts and thins out at the ends to be tied around her upper arms near the shoulders and down to her stomach. She wears a black mini skirt that is also tied behind her back, a long matching scarf and arm length fingerless gloves, and her legs are covered past her knees in what looks like shadow.

Personality
Raimeiki loves taunting and mocking Kureto as a possession-type demon. She takes pleasure in when she tells him to abandon all responsibilities and give into his greed and desires, often telling him about his lust for Aoi Sangū. She also easily gives up as shown when she was telling him to stop the sealing of Shikama Dōji; tricking him into needing more greed and desires. When Kureto succeeded, she was amused, telling him to keep going. Oddly Raimeiki also never told Kureto about her abilities other than basic electricity.

However, she also stated that she was desperately trying to protect Kureto from Shikama Dōji by sealing him, which shows her having some level of concern for Kureto.

History
Raimeiki's past is unknown except that she was a vampire and Shikama Dōji knew her. After becoming a demon, she got sealed and cursed inside a katana at some point, and formed a contract with Kureto Hīragi to become his cursed gear. He uses Raimeiki even in the light novels, this means that it was his primarily weapon since he didn't use any other cursed gear.

Post-Shinjuku Arc
During Kureto's interrogation on Yūichirō Hyakuya, the former uses Raimeiki to attack and overwhelm Yu.

Osaka Arc
Shikama Dōji greets Raimeiki as a long time friend when Kureto uses the blade to stab the six-winged demon. After getting possessed by Shikama, Kureto meets with Raimeiki in his mind. The demon confirms that Shikama was the First Progenitor of the vampires, but when asked about his greeting to her, Raimeiki ponders it for a moment before telling Kureto that she doesn't remember. Raimeiki then reminds Kureto that demons seek human greed and desires as they are unable to retain memories of their previous lives, and brings up Kureto's lust for Aoi and his desire to abandon all of his responsibilities. She also states that those desires are the exact reason he is so drawn to Guren and jealous of Mahiru which has Kureto question her loyalty. She tells Kureto that she is on his side, and though his father told him to never trust anyone, she says that he should trust her right now because she is desperately trying to protect him.

Raimeiki then disappears into shadowy smoke and sees the real Raimeiki, struggling to keep a set of double doors on the floor shut. She greets Kureto, explaining that he was talking with a shadow of her, and assures him that who he is seeing is the real her. Raimeiki explains that Shikama Dōji is trying to open a door into his heart, and upon seeing two chains escape through, she uses lightning to repel them.

Shibuya Arc
Currently Raimeiki is holding off Shikama Doji from invading Kureto's mind and body but according to Kureto she can't hold him forever due to him being stronger than her. When Kureto was later handcuffed he promotes being apathetic strengthens Raimeiki by holding off Shikama Doji more. When he laughed at Yu idiotic actions Shinya stated this also strengthens Raimeiki as well.

Forms and Abilities

 * Demon's Thrall: Can enter her host's dreams and memories to create nightmares to break the host's will in order to take over his body. This ability can only be used against its host.
 * Basic Form: Takes the form of a black katana with a glowing green streak down the middle.
 * Electricity: Raimeiki is able to enshroud her host with streaks of energy as both a defensive and offensive mechanism. Raimeiki is also able to use electricity to stimulate the muscles and increase speed; however this would tear the muscle fibers apart. When Kureto gave into his desires, Raimeiki gave off lots electricity within Kureto's mind.
 * Shadow Clone: Created one to communicate with Kureto while the real Raimeiki dealt with sealing Shikama Dōji.
 * Sealing: Created a seal within Kureto's mind to seal away Shikama Dōji, but due to him being stronger than Raimeiki, she needed to feed more on Kureto's desires to successfully hold down Shikama.

Kureto Hīragi
The head of the Hīragi family, he is the one who Raimeiki has a contract with. She was holding off Shikama Doji from completely possessing Kureto however according to Kureto she was not able to hold him off forever due to him being stronger than her, until Shikama Doji leaves Kureto's body. Kureto has no knowledge of Raimeiki abilities at first not until when it was shown to him.

Shikama Dōji
When Kureto stabbed Shikama Doji he greeted Raimeiki seemingly knowing her. Though this does not change the fact that she was trying to seal him off from invading Kureto's heart and taking over his body.

Trivia

 * Raimeiki is the only demon who has other abilities such as cloning when she first manifested and her sealing abilities that even Kureto didn't have knowledge about his demon unlike other hosts who knows their demon abilities.
 * When she first manifested in front of Kureto she didn't reveal to him that he was speaking with a clone until she disappeared into shadow smoke.
 * Raimeiki doesn't have any special techniques like other known demons such as Asuramaru, Kiseki-o, Gekkōin and Mahiru-no-Yo however her electricity is extremely powerful that it even overpowered Yūichirō Hyakuya and later when Shikama Dōji possessed Kureto, her electricity is augmented to the point of incapacitated Shinya.
 * She is hard to handle and requires great physical strength because of her electric charges that she produces when Kureto calls upon her.

Seraph of the End: Vampire Reign

 * "You always maintain impeccable self-discipline. And that's why you're so drawn to Guren. That's what made you so jealous of Mahiru. Both of them gave in to their desires so easily."--Raimeiki's shadow to Kureto, Chapter 58, "A Reason to Survive"
 * "Ha ha... Daddy dearest did tell you never to trust anyone, didn't he? But trust me now. Just this once... Because right now, the real me... is desperately trying to protect you."--Raimeiki's shadow to Kureto after Shikama Doji enters him, Chapter 58, "A Reason to Survive"
 * "Think what you please. I am your demon. Whatever your choice, I will accept it."--Raimeiki to Kureto, Chapter 58, "A Reason to Survive"
 * "Aha ha ha! Amazing! This is some amazingly powerful greed. That's it, Kureto. You aren't supposed to trust anyone, but what you desire more than anything is to have someone you can trust. Keep going, Kureto. Fall harder. Give in and accept that you are weak Then, speak what you want aloud."--Raimeiki to Kureto after Kureto decides to rely on Shinya and Guren, Chapter 58, "A Reason to Survive"