Transformation

Fed a lock of Kokushibo's hair, Genya convulses and breathes hard as Muichiro watches in alarm. His severed arm reattaches and his torso knits back together at astonishing speed while an eerie voice echoes in his mind. Astonished that a single lock could trigger such healing, he wonders how potent Upper Rank One's blood must be. As his body keeps recovering, he notices a broken fragment of the demon's sword nearby, and the voice returns, demanding to know how many Hashira Kokushibo has slain and warning him to keep them away. Genya realizes he is hearing Muzan and begins to fear what he may turn into if his transformation continues.

Fighting both Hashira, Kokushibo judges that Gyomei and Sanemi are likely the strongest of their generation, singling out Gyomei's extraordinary physicality and his finely made weapon, which lets the blind Hashira read his surroundings through the vibrations of his chain. Choosing to break Sanemi's sword first, the demon strikes at its side, but Sanemi intercepts and drives the demon's blade into the floor, his reflexes still sharpening despite his wounds. Gyomei cuts off Kokushibo's ear with an upward axe swing, and Sanemi separates the demon with Wind Breathing, First Form. The pair then combine Wind Breathing, Seventh Form, with Stone Breathing, First Form, shredding Kokushibo's kimono. When they rush in again for his head, they are suddenly covered in cuts before reaching him; Kokushibo reveals his sword now greatly extended with three additional cutting edges along its length, dismissing their combined attack as barely a scratch and threatening to finish everyone once the two are dead.

Having consumed a strand of Upper Rank One's hair, Genya heals at startling speed, and that rapid transformation lets him hear Muzan's voice.

Kokushibo identifies Sanemi and Gyomei as the strongest Hashira of the Taisho era, praising Gyomei and his weapon in particular. After the two strip away his kimono in a coordinated attack, Kokushibo unveils a new, larger multi-edged katana and severely wounds them both.

This Infinity Castle Arc chapter, part of Volume 20, marks an escalation on two fronts. Genya's accelerated regeneration and sudden link to Muzan raise the question of how far his demon-eating has pushed him, while Kokushibo's transforming, multi-bladed sword demonstrates that Upper Rank One has been holding back. The combined Hashira offensive, though impressive, is shown to be insufficient on its own.