Tōjū

The Tōjū are Zanpakutō spirits that Muramasa dragged into the material world, drawn from the blades of ordinary rank-and-file Shinigami. A Zanpakutō is meant to perish alongside its wielder, yet these spirits linger after their masters fall, hollowed out by the loss of the identity that once defined them. That emptiness twists them into savage, berserk creatures. The Twelfth Division's own captain, Mayuri Kurotsuchi, coined the name for them and judged them something entirely unprecedented, neither sword spirit nor Shinigami nor Hollow.

Because a rampaging Tōjū draws on its blade powers at full tilt, Mayuri likens the state to a permanent Bankai, meaning even a feeble Zanpakutō turns dangerous once it snaps. Their reserves of Reiatsu are finite, however, and when that energy runs dry they collapse back into simple swords. Many prolong their existence by merging with other beings: fusing with a Hollow, as Tōshirō Hitsugaya deduces, magnifies their strength and blends the two sets of powers, while binding to a Rukongai villager leaves the host bald, red-eyed, and barely coherent, sapping the spirit's own might in the bargain. Possessing a human instead lets a Tōjū mask its presence and speak to its host mind to mind. Not all of them break at once; some cling to their sanity for a time, and Narunosuke shows that kindness can briefly pull a Tōjū back from the edge, even as the absence of a master slowly and painfully unmakes most of them.

The Tōjū first surface soon after Muramasa's death, when two of them ambush Rukia Kuchiki at a Kuchiki flower-viewing gathering, and she survives only with help from the spirits Sode no Shirayuki and Senbonzakura. Later examples include Narunosuke, who keeps his mind long enough to bond with another, and Kirikaze, who preys on fellow Tōjū to drain their power and grow stronger before his death finally ends the threat and returns the scattered blades to their sealed forms.