Kaigaku (獪かい岳がく, Kaigaku?) was a supporting antagonist in the Infinity Castle Arc of Demon Slayer: Kimetsu no Yaiba. He was a demon affiliated with the Twelve Kizuki, having held the position of Upper Rank Six (上じょう弦げんの陸ろく, Jōgen no Roku?), replacing Daki and Gyutaro after their deaths.

Kaigaku was a former Demon Slayer and Zenitsu Agatsuma's senior disciple under the former Thunder Hashira, Jigoro Kuwajima. However, sometime during the Hashira Training, Kaigaku went on a mission and encountered Upper Rank One, Kokushibo, quickly surrendering to him to save his life and later becoming a demon.