Dark History! The Worst Shinigami Is Born.The flashback continues and reveals that Kōga killed the people who had framed him, but after Ginrei confronted him, he went insane and began killing anyone he perceived as an enemy. Muramasa tried to reach out to Kōga but eventually was no longer able to hear his voice. Kōga was finally defeated and sealed away by Ginrei and Yamamoto when Kōga's call for Muramasa went unheard. In the present, Muramasa asks why Kōga stabbed him, as he had worked hard to bring about his return, but Kōga responds that zanpakutō are tools that obey their masters' commands. He tries to finish off Muramasa, but Byakuya steps in, saying that he is no longer worthy to be called a Soul Reaper.