Muramasa is fighting a losing battle to keep his Reiatsu in check. He repeatedly calls for his master in vain. Instead of Kōga, hundreds of Hollows arrive, attracted by his Reiatsu. Ichigo tries to fight them off with Getsuga Tenshō, but Uryū's arrows prove more effective, for this work. Chad and Orihime join the two and Rukia just in time for Orihime to protect the group from a Cero shot by a Menos, using Santen Kesshun. As the group stares in disbelief, Muramasa implodes into a spiritual black hole.
Kōga and Byakuya's clash releases enough energy to melt the thick sheet of ice that formed over the pond after Kōga's spell. Mist spreads over their battleground. Byakuya staggers, but Senbonzakura supports him. Kōga is mortally injured, and has to support himself with his spear to keep himself from falling. Refusing to admit defeat, he calls for Muramasa, but to no avail. His Zanpakutō's name is the last word to escape his lips, before he topples over into the water.
The horde of Hollows attracted by Muramasa's explosion of Reiatsu are now hopelessly dragged into him and absorbed. The massive Gillians are hoisted into the air and sucked into the vortex. Once all the Menos are absorbed, there is a flash of light followed by an explosion. When the smoke from the explosion clears, Muramasa appears in a new form, that of a Hollow. Rukia explains that Zanpakutō share their body and soul with their masters, bonding with their souls and living in symbiosis with them. Therefore, Muramasa had to rely on energy absorbed from Hollows to stay alive. Due to Kōga's betrayal, that Hollow energy has now spun out of his control, giving him this form. Muramasa continues to release his Reiatsu, and the group realizes that they must stop him before it engulfs all of Karakura Town. Muramasa attacks, but the group is too slow to respond to his speedy offense. Ichigo can only block his attack, and he proves far too agile for Uryū's arrows. When Muramasa goes for Rukia and Orihime, he is encountered by Chad, who blocks him with his Brazo Derecha de Gigante and throws him off course. Ichigo's subsequent attack is blocked. After a short pause, in which Muramasa attempts to regain his self control, he charges a Cero and launches it straight at Rukia and Orihime. The two are saved by the arrival of Byakuya and Senbonzakura, who block the Cero.
Byakuya insists that his injuries are not as serious as the need to deal with Muramasa, and states Muramasa must have completely turned into a Hollow to be able to fire a Cero. Muramasa renews his struggle to control the Hollow powers within him. Orihime runs towards the struggling spirit and pleads with him to stop fighting, believing that the Hollows have not taken over him yet. The confused Muramasa calls for Kōga again, despite his transformation. Orihime, still pleading, steps even closer. Just as it appears as if Muramasa had won, the Hollow takes over again and Muramasa attacks Orihime. She blocks instinctively with Santen Kesshun but the shield breaks and Orihime's leg is injured and she is thrown back. Muramasa's next attack is blocked by Ichigo, who proceeds to attack. The two spar for a while before Muramasa unleashes a barrage of Bala, which Ichigo avoids by Hollowfying. Ichigo responds to Muramasa's next Cero with a Getsuga Tenshō, which hits him. Muramasa is hurt, but quickly recovers and begins to open a Garganta in the sky, which also attracts more Hollows. Chad, Uryū, Byakuya and Rukia fight off the Hollows, while Ichigo reaches Muramasa and manages to hit him with a point blank Getsuga Tenshō.
Badly hurt, Muramasa falls to the ground. Ichigo lands next to him and to his surprise Muramasa suddenly transforms again, engulfing Ichigo with his shifting mass. Muramasa transforms into a huge dome-like structure that emits Menos which attack the group. Byakuya releases Senbonzakura and dispatches most of the Menos, but one chases Rukia and Orihime. As it is about to fire a Cero, Sode no Shirayuki arrives and destroys it with Tsugi no mai. Sode no Shrayuki is accompanied by some of the strongest officers in the Gotei 13, including Captains Suì-Fēng of the 2nd Division, Hitsugaya of the 10th Division and Komamura of the 7th Division, all reunited with their Zanpakutō.