Webduring the hashira training arc, a bird brings zenitsu a letter explaining what happened, and shortly after we see him being all serious. Though if i remember correctly it's not. Webas revealed in demon slayer chapter 144, titled successors, zenitsu’s letter brought him news about the sudden death of his master and former thunder hashira, jigoro. Webthe letter conveyed the news that zenitsu’s former master, jigoro kuwajima, the former thunder hashira, had passed away. Kuwajima wasn’t just any. Webas revealed in demon slayer chapter 144, titled successors, zenitsu’s letter brought him news about the sudden death of his master and former thunder hashira,. Webwhile many are motivated by early tragedies, zenitsu’s true purpose emerges later, sparked by a personal loss. This newfound purpose is a powerful catalyst,.
