Muku

was a Kusagakure shinobi that appears in Naruto 5: Blood Prison.

Background
Muku lost his mother as a baby and was raised by his father, Mui, the guardian of the Box of Ultimate Bliss. He was regarded as a prodigy of his village and, therefore, his chakra was chosen to open the box in hopes of returning Kusagakure to its former glory. The day before it happened, Muku promised his best friend, Ryūzetsu, that he would return no matter what happened. Unfortunately, Muku's chakra wasn't enough and he was sucked into the box instead where he spent ten years trapped in despair and grief.

Personality
As a child, Muku was a cheerful individual that loved his father, Mui, dearly. His greatest wish was to live a peaceful life with his father and his best friend. However, after spending years inside the Box of Ultimate Bliss, he reemerged as an apathetic, cold and cruel person; this is shown when Muku was not hesitating in the slightest to run his hand through his father's chest.

Appearance
Muku has extremely pale skin which contrasted with his jet-black hair and grey eyes. He wore a blue kimono shirt with the sleeves rolled up, a scarf around his neck and black arm-warmers. He also wore a pair of blue pants and sandals on his feet. After emerging from the Box of Ultimate Bliss, he was noticeably older and taller. His hair was longer and had dulled in colour and he was wearing the same clothes as he had when the box was open.

Abilities
Muku was stated to be a prodigy of his village. He was very proficient with Fire Release techniques, allowing him to make fire-like apparitions to attack his enemies with Fire Release: Demon Lantern. He has also been seen to be strong enough to pierce his father's chest bare-handed. He seems to have a great amount of chakra, as his father used him in an attempt to open the Box of Ultimate Bliss, though it was not enough to accomplish the feat.

Plot Overview
As a young man, Muku was sealed into the Box of Ultimate Bliss as a sacrifice in order for his father to open it. This was done in the hopes of asking the box to grant them the wish of reviving Kusagakure to its former glory. Grief-stricken by having to do this, Mui sought for a long time to reopen the box to ask for his son back and when this day came to pass, Muku emerged from the box and stabbed his father straight through the chest with his bare hands. After seeing his friend Ryūzetsu again he transforms into Satori who begins to go on a rampage. Ultimately the beast is stopped by the combined efforts of Naruto Uzumaki and Muku's own father who brands him with the Fire Release: Great Fire Heavenly Prison technique. After reverting to a human form, Muku opens his mouth and unleashes a final attack on his father, killing him before activating the Fire Release: Demon Lantern and engulfing himself in flames. Seemingly regaining some sense of himself, he apologises to Ryūzetsu for being unable to keep the promise he made to her to return no matter what and states that at least now, he and his father could rest peacefully. As he is engulfed in flames, he returns to the box which closes.

Trivia

 * His name means "purity" or "innocence".