Spoiler-Safe Summary

safe read

Mayuri investigates mysterious phenomena involving zanpakutou, leading to unexpected attacks on their storage. Ichigo encounters complications with Muramasa and faces off against Senbonzakura, just as Byakuya reveals a shocking allegiance, altering the dynamic among key characters.

Full Plot Summary

spoilers

Mayuri experiments on Gegetsuburi and discovers that the zanpakutou can only return to their owners' control once they are defeated by their owners. Rangiku and Momo send their zanpakutou back to the fourth division barracks, but an unknown assailant attacks the cart carrying them. Ichigo meets with Rangiku and Momo, and then reaches Muramasa, who is having difficulties using his abilities in his current body. Ichigo attempts to attack Muramasa but is stopped by Senbonzakura. 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, and then disappears with Muramasa and Senbonzakura.