Muramasa's True Identity Revealed

With Koga defeated by Byakuya, the Zanpakuto spirit Muramasa loses his grip on himself. Robbed of the master he served, he begins swallowing the Hollows drawn to his surging power, straining his very existence past its limits to cling to a physical body. Ichigo, Rukia, Uryu, Orihime, and Sado fend off waves of Gillians and larger Hollows as Muramasa's energy condenses into a dark sphere.

Nearby, the duel between Byakuya and Koga ends. Koga, refusing to believe it, calls out for Muramasa but gets no answer before sinking to the bottom of the lake. Senbonzakura catches the wounded Byakuya and reflects that Koga's great strength curdled into a curse because ambition consumed him, the mirror opposite of Byakuya, who accepted disgrace to shield Soul Society.

The sphere detonates, and Muramasa emerges reshaped into a humanoid Hollow. Rukia explains that a spirit coexists with its master's soul, so Muramasa needed all those Hollows as a replacement source of energy to survive Koga's death.

Muramasa turns on the group, striking fast and firing Cero and Bala. Byakuya's blade petals shield Rukia and Orihime as the returned captain rejoins the fight. Blue energy crackles around Muramasa, and he clutches his head, battling the Hollows he absorbed. Orihime senses he has not been fully consumed and steps forward to plead with him, but he lashes out and shatters her shield.

Donning his Hollow mask, Ichigo trades blows with Muramasa and blasts him with a point-blank Getsuga Tensho, only for the spirit to regenerate and swell into a vast black-red dome that engulfs Ichigo. The overwhelming energy cracks the sky itself, and Uryu warns that a Garganta is tearing open above them.

As Gillians spill from the fractured heavens, Sode no Shirayuki appears and freezes one solid, then descends to Rukia with several other Soul Reapers and their manifested Zanpakuto spirits standing ready to help.

This is an anime-original installment of the Zanpakuto Unknown Tales arc with no manga chapters behind it. It concludes the duel between Byakuya and Koga Kuchiki and stages the return of the rebel Zanpakuto spirits.

A closing Arrancar Encyclopedia segment shows Tosen fretting over a sudden drop in the Menos population while Gin wonders aloud whether someone has been poaching them.