If you've been watching the Hashira Training arc, you probably observed that Zenitsu changed as soon as he received an enigmatic letter. Its secretive contents are the key to a devastating discovery. Though the anime hasn't shown anything yet, the manga thankfully offers us a sneak peek. We're going to examine what Demon Slayer Season 4 Episode 7 says about Zenitsu's letter. But be advised, there are manga spoilers up ahead.
What did Zenitsu write in Demon Slayer's letter?
Hellcat Killer As Zenitsu engages Kaigaku in a contentious debate in Chapter 144, it is confirmed what was said in his letter. According to the letter, Jigoro Kuwajima, Zenitsu's non-blood grandpa, killed himself after seeing his former pupil, Kaigaku, transform into a demon.
Formerly known as Thunder Hashira, Kuwajima was the trainer of both Zenitsu and Kaigaku. Like his friend, Kaigaku later turned into a Demon Slayer. However, he ultimately betrays his loved ones by bringing a demon into their house in an attempt to save his own skin, rather than following a road of righteousness. The background of Stone Hashira was also disclosed in the Season 4 episode. After that, Kaigaku succumbs to the allure of unrestricted power and assumes the role of an Upper Rank Six demon.
Jigoro becomes consumed by guilt as a result of this betrayal since he thinks he is the one who created the demon. Even worse, he was alone himself when the seppuku act—which usually calls for another person—was carried out. But Kuwajima endured for a long time before passing away since no one else could bring him to an end.
In Season 4, Episode 7, Zenitsu's behavior shifts since he becomes almost heartless upon learning of his loving master's demise. Fortunately, because the disclosure is just a few chapters away from where the show is, it shouldn't take long for the anime to cover the letter as well.