Utakata

was a shinobi from Kirigakure and the jinchūriki of the Six-Tailed Slug. The Six-Tails has been captured and sealed by Akatsuki, causing Utakata's death when the beast was extracted. While the events surrounding his capture and death are currently unknown, Utakata and the Six-Tailed Slug appear in a currently-ongoing filler arc in the anime, even though they were not created for the filler arc.

Personality
Kishimoto described Utakata as "charming." Utakata is usually depicted with a stoic, emotionless look. The only time he has shown any emotion at all, that emotion being anger, was from his desire not be called, later saying he is not foolish enough to be titled "master." Utakata is a loner who shows no emotional attachment, yet has a strong sense of honor, and is determined to repay his debts to others.

Appearance
Utakata is a tall, thin young male with dark brown, shoulder-length hair with amber-colored eyes. He wears a long blue kimono with an orange sash belt. He carries a bamboo jug which is filled with a soap solution inside his kimono that's tied on by his orange sash. His kimono sports a small crest near the back of his neck that appears to be a simplified image of three bubbles.

Abilities
Utakata fights using ninjutsu from the  of ninjutsu, using a unique kind of bubble-blowing relic. In the anime, it is shown he is able to stand inside the bubbles he blows and can float along inside them. He can also trap his enemies in his bubbles and kill them with his technique, Ink Bubble Explosion, or by drowning them quickly. He is shown to be able to fill the bubbles with blinding gas and slime. He is also shown to be highly evasive, effortlessly dodging all of Naruto's attacks and attacks from Nangō, Akaboshi, Benten, and Chūshin.

Six-Tailed Beast arc
Sometime prior to the events of the Six-Tailed Beast arc, although it is unknown how long, Utakata trained under an unknown master, who taught him how to use Bubble Ninjutsu. However, Utakata's master eventually betrayed him, sealing the Six-Tailed Slug inside of him. After this, Utakata gained a fear of betrayal between master and student, and became a wanderer, constantly fighting off people going after him for the living weapon he had been made into.

One day, he was attacked again in front of a girl named Hotaru. While defeating his attackers, he was injured. Believing that Utakata had saved her, Hotaru took him to her family's fort for treatment. After he recovered, Utakata was begged by Hotaru to train her in his ninjutsu, to which he refused, not wanting to become anyone's master. Wishing to repay the debt of having his life saved, Utakata agreed to make sure Hotaru and her grandfather's secret jutsu would safely be delivered to her clan's village.

Along the way, though, he met Naruto Uzumaki and his team, who had also been assigned to protect Hotaru. Seeing that the Leaf ninja were strong, he felt that he could trust them to guard Hotaru without him, freeing him from his debt. He then left, despite Hotaru's pleas for him to stay, as he noted that he was not foolish enough to want the title of.

Later on, he was seen resting under a tree, eventually falling asleep and having a dream regarding his past with Hotaru at the fort, which turned into a nightmare about his own master's betrayal. Shortly after awaking from this nightmare, Utakata spotted a flicker of a shadow, and decided to investigate. He came across a group of bandits, none other than Akaboshi's team, who were talking about the forbidden jutsu. Utakata confronted them and mused about taking the jutsu for himself, if it was so tantalizingly powerful. He then proceeded to fight them, easily besting them and their jutsu, until, however, they cornered him with a barrier, which then exploded with Utakata still inside.

Trivia

 * refers to bubbles on the surface of a liquid. Idiomatically, it also means "transient," "ephemeral."
 * In the anime, Utakata and the Six-Tails remain yet to be captured by Akatsuki, as the sealing statue wasn't shown having 7 of 9 eyes yet (2 others had to be captured in the manga). In order to avoid conflict with the manga, it seems inevitable that, by the end of the arc, Utakata will have been captured and the Six-Tails extracted, resulting in his previously-unseen death, in a manner similar to the Three-Tailed Giant Turtle.
 * His yet-unnamed musical theme is a remix of Guren's theme.