Muku

Pale skin sets off Muku's grey eyes and jet-black hair. In boyhood he favoured a blue kimono top with its sleeves rolled back, a neck scarf, dark arm-warmers, blue trousers, and sandals. The ten years shut inside the box left him taller, his complexion ghostly white, his hair lengthened and faded, the very same outfit now hanging off him in tatters.

The boy Muku was sunny and affectionate, adoring his father and wanting little more than a calm life beside him and his closest friend. Ten years locked away drained all that warmth, leaving someone frigid and pitiless, apparently so bitter that he could drive a hand through his father's ribs without a second's pause. Most of that was Satori's corruption rather than the true Muku, who survived beneath it and rose at the last to fight off the demon, to beg Ryuzetsu's pardon for the vow he could not honour, and to embrace his own death so he and his father might rest at peace.

Muku lost his mother in infancy and was brought up by Mui, his father, whose charge was to watch over the Box of Ultimate Bliss. Hailed as a prodigy in his village, he was picked so that his chakra might unseal the box and bring Kusagakure back to glory, and the night before, he vowed to his friend Ryuzetsu that, come what may, he would be back. His chakra fell short; the box drew him inside instead, and he wasted away there across ten years, every bid to break free coming to nothing. A genuine talent, he handled Fire Release with ease, summoning flame-like phantoms and the Demon Lantern technique, and hit hard enough to run a man through and cleave another in two with bare hands. Bound to the demon Satori, he picked up wings, dizzying speed, a feel for an enemy's bloodlust, and salvos of energy orbs and piercing feathers.

Once Mui at last reopened the box, Muku came out fully grown, and as his father pleaded for forgiveness the reply was a hand punched through his chest and Kazan cut down, followed by the flat remark that he should never have been dragged back. Catching sight of Ryuzetsu tipped him into Satori's shape, and his knack for reading fear and killing intent let him weave clear of everything Naruto, Killer B, and the gathered Leaf ninja hurled his way. The turning point arrived when Naruto grasped that the demon could not feel the fearless Ryuzetsu; he landed a hit, and after Mui seared Satori and Naruto struck home with the Wind Release: Rasenshuriken, Muku briefly came back to himself. He took his father's hand, then loosed one last strike that killed Mui before folding himself into the Demon Lantern's fire, offering Ryuzetsu his apology as his body burned to ash and Satori sank back into the box, which sealed shut.