In the aftermath of the Muramasa incident, the Shinigami return to Soul Society, but they find that their respective Zanpakutou spirits are still able to take human form. To complicate matters, also on the loose are what Kurotsuchi calls Toujuu (lit. sword beast), which are materialized Zanpakutou who went berserk after their masters were killed trying to subdue them. Of the two that appear, Senbonzakura helps Sode no Shirayuki defeat one of them, and Rukia wielding Sode no Shirayuki eventually defeats the other, strengthening their relationship in the process. Kurotsuchi takes in the latter one for research, and when Ukitake reveals that there are reports of more, Sode no Shirayuki reassures Rukia that the Zanpakutou will help with this matter.