What Happened To Zenitsu In Demon Slayer? Explained

In episode 7 of season 4 of Demon Slayer, Zenitsu’s mood takes a complete turn from his normal friendly but timid nature. What was the catalyst that sparked this dramatic change in Zenitsu and what does it mean going forward?

There will be spoilers ahead for anyone who has not read the Demon Slayer manga.

What Changed Zenitsu in Demon Slayer?

At the beginning of the episode, Zenitsu’s sparrow Chuntaro brings him a letter. Zenitsu tries to brush him off but the little bird is insistent, meaning that whatever was in that letter was important. The next time we see Zenitsu is when his demeanor does a one-eighty and gone is the energetic and anxiety-filled character we know. It is this letter that changes everything for Zenitsu.

In the letter, Zenitsu learns that his teacher Jigoro Kuwajima has killed himself through Seppuku, one of the most painful and drawn-out deaths with no one to give him the mercy of a quick release from the pain. Jigoro Kuwajima, a retired Hashira of the Thunder Breathing technique, learned that his other student had defected from the demon slayers and had become a demon himself. To make matters worse, this student had mastered all but the first form of the Thunder Breathing technique and took that knowledge to harm many innocent people. The overwhelming guilt Jigoro felt led to his decision to atone for his mistakes and the acts of his former student.

What Was The Cause Of Zenitsu’s Tragic News?

The route of every tragedy, revealed and hinted at, in episode 7 is Kaigaku, Jigoro’s former student who was taught along side Zenitsu. We learn earlier on in the episode that Kaigaku has a history of betrayal through Gyomei’s flashback. During his childhood, Kaigaku was one of the orphans who was under Gyomei Himejima’s care but in an effort to save his own life, led a demon into Gyomei’s temple and caused the grewsome death of the other orphans.

However, neither the contents of the letter given to Zenitsu nor Kaigaku being the cause of Gyomei’s traumatic backstory is revealed until later on in the Infinity Castle arc. Zenitsu will get his chance to confront his ex-fellow student in a one-on-one fight. And this time, Zenitsu will be awake for every moment of it.

Kaigaku is the center of recent and past traumatic events in Demon Slayer. Find out exactly who Kaigaku is and the motivations behind his devastating choices.