After dismissing Sode no Shirayuki, Muramasa proceeds to lecture Ichigo on how Zanpakutou are souls born inside the heart of the Shinigami. Muramasa feels that the Zanpakutou aren't part of the Shinigami though and are their own separate entities, and he also reveals that he used Rukia to lure Ichigo here. When Ichigo tries to fight him, Ichigo finds that he's unable to land any of his attacks, even his Getsuga Tenshou, and Muramasa counterattacks by casting a disorienting spell. With Ichigo unable to do anything, Muramasa is able to separate Zangetsu from him. Ichigo is no longer in bankai form and realizes that Zangetsu is now standing in front of him, and Ichigo barely has any time to defend himself before Zangetsu attacks.
While the battle is going on, Captain Kurotsuchi is doing research regarding the Zanpakutou and has his findings so far reported to Captain Unohana and Isane. Just as it looks like Ichigo is finished though, he re-emerges and his Hollow side burst out and launches a furious assault. He's able to match Zangetsu move for move, and when Zangetsu appears to hurt him, Ichigo just becomes even more Hollowfied. After Hollow Ichigo overwhelms Zangetsu with a cero blast, Muramasa re-enters the fight, but his attack is quickly healed up. The Hollowfied Ichigo seems ready to take on Muramasa, however Ichigo refuses to give up his body to his Hollow side, and he fights to regain control of himself. He succeeds, but he's too exhausted to fight afterward, and he collapses in front of Muramasa.