Muku was a shinobi from Kusagakure from the Naruto Shipudden film, Naruto 5: Blood Prison. He was the son of the Hozukijo prison castle's master, Mui. He was regarded as the prodigy ninja of his village and his chakra was chosen to open the Box of Ultimate Bliss, that was told to grant wishes, including Kusagakure's ambition to become a superpower. Muku's chakra was insufficient for the box and was absorb to the box instead. Before risking himself for the opening of the box, he promised his best friend Ryuzetsu, to come back safely. Later he was freed from the box by his father. The Box of Ultimate Bliss corrupted him causing him to pierce his arm through Mui's chest and then transforming into Satori.
He was turned back to normal by the combined efforts of Naruto and his jaded father. He used his Fire Release: Demon Lantern jutsu in order to activate the seal his father placed on him, killing himself before Satori regain control of his body. His father was killed when Satori tried to regain control. Before he died, he apologizes to Ryuzetsu for not keeping his promise and that at least he and his father can rest peacefully.