Tokyo Revengers Season 1 Episode 18

Back in present day, Draken tells Takemichi that Kazutora ends up killing Baji at the Bloody Halloween, the fight against Toman and Valhalla, and Mikey ends up killing Kazutora. Because of that, Mikey falls into darkness, and Toman is taken over by Valhalla, which leads to the evil organization that it currently is now, led by Kisaki. Takemichi goes back to the past with a new mission: to protect Baji so that this tragedy doesn't happen.