Kaigaku

Lore & Background

Kaigaku was Zenitsu Agatsuma's former senior in the Demon Slayer Corps. After an encounter with Upper Rank One Kokushibo, Kaigaku became the new Upper Rank Six. His betrayal of the Corps led to their master Jigoro committing seppuku. During the battle in the Infinity Castle, Zenitsu faced Kaigaku, angered by his lack of guilt over this betrayal. Kaigaku voiced his frustration at being compared to Zenitsu during their fight. He was ultimately killed when Zenitsu used a self-taught Thunder Breathing form.

In Their Own Story

The clash within the Infinity Castle was swift and brutal. Zenitsu Agatsuma faced his former senior, Kaigaku, who had become the new Upper Rank Six after an encounter with Kokushibo. Zenitsu's anger burned not from personal rivalry, but from Kaigaku's complete lack of guilt over their master Jigoro's seppuku—a suicide forced by Kaigaku's betrayal of the Demon Slayer Corps. Kaigaku, in turn, voiced his frustration at being constantly compared to Zenitsu. Their battle ended when Zenitsu unleashed a self-taught Thunder Breathing form, cutting Kaigaku down. After the fight, Zenitsu passed out and momentarily entered the afterlife, where Jigoro reaffirmed that he had always been proud of him.

Reader's Guide

Kaigaku serves as a dark counterpart to Zenitsu Agatsuma, representing the path of betrayal and ambition. He was Zenitsu's former senior in the Demon Slayer Corps, but abandoned his oath after an encounter with Upper Rank One Kokushibo, becoming the new Upper Rank Six. His betrayal directly caused their master Jigoro to commit seppuku. In the Infinity Castle, Zenitsu confronted Kaigaku, driven by anger at his lack of remorse. Kaigaku, frustrated by comparisons to Zenitsu, fought back but was ultimately killed by Zenitsu's self-taught Thunder Breathing form. His death marked a turning point, allowing Zenitsu to find closure and hear Jigoro's final words of pride.

Did You Know?

• Kaigaku became the new Upper Rank Six after an encounter with Upper Rank One Kokushibo.
• His betrayal of the Demon Slayer Corps led to their master Jigoro committing seppuku.
• Kaigaku was killed by Zenitsu using a self-taught Thunder Breathing form.
• After his death, Zenitsu momentarily entered the afterlife where Jigoro reaffirmed his pride in him.
• Kaigaku voiced frustration at being compared to Zenitsu during their battle.