Kaigaku

Kaigaku was a member of the Twelve Demon Moons, holding the position of Upper Moon 6. He was originally a Demon Hunter and member of the Demon Killing Corps as well as Zenitsu Agatsuma's senior student when they were being taught by Shihan.

Appearance
As a human Kaigaku was a fit young man who had black hair and turquoise eyes. As a demon he gained black, flame-like markings on his face, fangs, and pale skin. As an upper moon, he gained kanji on his eyes.

He usually wears a black kimono over his demon hunter uniform, that has yellow markings on it.

Personality
Kaigaku is a very prideful, to the point that he’ll serve anyone who recognizes his strength. He’s very intelligent learning breathing techniques almost flawlessly. His ingenuity was only strengthened by his demonic transformation, as he used the special powers of his blood to improve his breath style. He hates weakness, especially when it obstructs something he wants, as seen with Zenitsu.

History
Kaigaku was an orphan and a thief, who had to eat scraps and steal to survive. This established a certain belief in his head, he started to believe that strength was the only thing worth respecting, and those who can‘t see true strength or are too weak aren’t worth respect. He taken in by Shihan, along with Zenitsu, and taught the Breath of Thunder style. He became determined to become Shihan’s successor and the new Thunder Pillar. Shihan however said that he and Zenitsu would become his successor. This, along with his weak power and timid nature, cause him to hate Zenitsu.

Later he went on a solo mission to hunt down Kokushibou, though he was to weak to even scratch him. After the defeat he kneeled before Kokushibou and begged for his life. Kokushibou offered his blood to turn Kaigaku into a demon, which he accepted. As a demon Kaigaku ate a multitude of people and came abnormally powerful. And after the deaths of Daki and Gyuutarou, became upper moon six of the Twelve Demon Moons.