Bleach: Season 1, Episode 240

1 - 240: Byakuya's Betrayal

Mayuri experiments on Gegetsuburi, and discovers that the zanpakuto only return to their owners' control if they are defeated by their owners. Momo and Rangiku send their zanpakutos back to the 4th division barracks, but the cart carrying them is attacked by an unknown assailant. Ichigo meets with Momo and Rangiku, then reaches Muramasa, who is having difficult using his abilities in his current body. Ichigo fights Senbonzakura, and gains the upper hand before Byakuya arrives. Byakuya reveals that he has joined Muramasa as part of following his internal desire to protect his pride, then attacks Ichigo.