In his physical form, Narunosuke is a tall, thin, pale young man. He has straight indigo hair. It is long on top and cut short on the sides, with several locks hanging over his face. His eyes are Tyrian purple, a bright red-violet. His skin is pale and he has sharp features. All in all, he quite resembles his Shinigami.
He wears a plate of white armor with gold trim on his left shoulder, tied in place with a white sash; and a white robe, tied with a long Tyrian purple sash. On his left wrist is a black snake-like bracer.
Beast Swords arc
Muramasa and Kōga have been defeated. The Gotei 13 are exterminating the Tōjū, Zanpakutō spirits who have gone insane following their masters' deaths. Haineko, on a mission with the 10th Division, finds a Tōjū that is still sane and appears injured. She is lovestruck at first sight and cannot bring herself to kill him. She instead takes him to an isolated house deep in the forest and treats his wounds. There, he tells her that his name is Narunosuke.
Although Narunosuke's wounds are healed, he suffers migraines that cause him to lose control of himself. These are becoming worse and more frequent.
After food and medicine go missing from the 10th Division storage, Rangiku follows Haineko and finds Narunosuke. Haineko tries to defend Narunosuke, but he loses control, attacking Rangiku and Haineko. She realizes that she cannot save him and embraces him. He regains his sanity for a brief moment before he is destroyed by her ash cloud. Narunosuke reverts to his sword form, which shatters.