Kaigaku

Blood Demon Art: Thunder

As the new Upper Moon Six, Kaigaku retains his mastery of Thunder Breathing swordsmanship even as a demon and fuses it with a lightning-based Blood Demon Art, striking with blinding speed. In Infinity Castle Part 1, Zenitsu finally defeats and kills him in single combat.

Kaigaku retains a build similar to his human life, sharp-featured and dark-haired, wearing tattered black robes over a muscular frame, but his demon transformation gives him glowing red-gold eyes and claws that crackle with electricity.

Kaigaku is prideful, resentful, and consumed by jealousy of his former junior Zenitsu's talent, having betrayed the Demon Slayer Corps and killed his own master out of wounded ego. As a demon he is even more arrogant and dismissive of his former comrades.