Kaigaku is a major character from Demon Slayer: Kimetsu no Yaiba, known for being a supporting antagonist and a demon affiliated with the Twelve Kizuki, holding the position of Upper Rank Six. He is a former demon slayer and Zenitsu's senior fellow disciple, who betrayed his comrades and fled from a demon in order to save himself. This act led him to be turned into a demon by Kokushibo. He is also a user of Thunder Breathing and has a powerful Blood Demon Art.