In a flashback several centuries ago, it is revealed that Kōga was part of the Kuchiki clan as the son-in-law of Ginrei Kuchiki and was overconfident in the abilities of his zanpakutō. He helped put down a rebellion of Soul Reapers, but some grew suspicious of his power and had him attacked. He cut down his attackers, but he was framed for killing his own allies by a group of jealous high-ranking Soul Reapers. He was imprisoned as a result, but he escaped with Muramasa's help. In the present, Kōga awakens, repelling Ichigo and Rukia, then suddenly stabs Muramasa.