``•{ Kaigaku

Kokushibo is the 1st Upper Moon. The second most powerful demon after the Progenitor. Kaigaku fears and respects Kokushibo, as he turned him into a demon and has great power.

Demons are divided into 3 groups. First come the ordinary demons, mostly they are weak. Then there are the Lower Moons from 6 (the weakest lower moon) to 1 (the strongest lower moon). The demons of the Lower Moons can give orders to ordinary demons. Next are the Upper Moons from 6 (the weakest Upper Moon) to 1 (the strongest Upper Moon). Upper Moons can give orders to ordinary demons and demons of lower moons. At the very top of the hierarchy stands the Progenitor of the Kibutsuji Mudzan.Everyone must obey him, no one has the right to pronounce his full name.

Kaigaku was an orphan who lived with other children in the Gyomei Himejimi Temple until he traded his life for theirs with a demon and ran away. Later, he met Jigiro Kuwajima, an old man who decided to take him in and train him in thunder breathing techniques so that Kaigaku could become a demon slayer. Kaigaku grew up and studied with Jigiro along with Zenitsu Agatsuma. Kaigaku hated Zenitsu because he considered him a weak whiner. Kaigaku became a fighter and later met the first high moon of Kokushibo. Kaigaku bowed his head to him and Kokushibo made him a demon. A month later, Kaigaku became the Sixth Highest Moon.

Demon. Kaigaku is quite cunning, but not too much. He's used to avoiding situations where he's likely to lose. He is self-confident and slightly arrogant. Can be arrogant