First appearance: Chapter 48

Age: 17

Height: 176cm

Weight: 70kg

Type: Dou

Type: Katsujin Ken (Satsujin Ken while in Yomi)

Yomi Symbol: Moon

Martial Arts: Chinese Kenpo (Pī Guà Quán and Bā Jí Quán)

Tanimoto Natsu was the former Sixth Fist of Ragnarok, and is the disciple of Ma Sougetsu, an unofficial captain of the Shinpaku Alliance, the holder of the Moon Symbol of Yomi and is one of Kenichi's main rivals.

He is a tall fair-skinned man with dark blue eyes, spiky yet wavy chin-length blond hair, with a well-defined built and respectably muscular frame. A noticeable trait of Tanimoto is the look his eyes during the situation he is in. While maintaining his kind-demeanor, his eyes are big and calm. When angered or fighting, his eyes narrow with small cat-like pupils. A recurring theme in his appearance is that he is considered quite handsome by nearly all girls near his age.

Tanimoto typically wears a white-grey shirt with a red cross on it, similar to the design of a crusader, at school. As Hermit, Tanimoto wears a dark hood and cloak with arm bands and leather boots, with pentagrams sewn into his leather gloves. Originally, the symbols on his gloves were that of the Roman numeral number six (VI). However, after his defection from Ragnarok, he changes the symbols to a pair of pentagrams.

Tanimoto is the president of the drama club at Kenichi's school and is considered to be the school's "prince", pretending to be a kind and soft spoken student, which plays well seeing how he is popular with both teachers and students. To further the illusion that he is a gentle and kind person, he makes sure not to reveal his muscular build, and even claims that the sun is bad for his skin just to prevent his body from being shown off during the camping trip.

He claims to have only joined the drama club to practice deceiving others, and is only nice because he perceives popularity as a way to control people. In truth, he is cold, ill-tempered, and extremely prideful. He also whacks Kenichi and Nijima or threaten them whenever they try getting too close (both figuratively and literally). Tanimoto also can't stand it when Kenichi calls him Natsu-chan to which he irritably responds "Who's Natsu-chan?!"

The words left by his sister Kaede as a request not to lose affected him tremendously, to the point where he will continue to fight even if he is knocked unconscious as seen in his second fight with Kenichi, and later in his death match with Chou Enshin. However, this also leads to him refusing to quit anything such as when he stubbornly refuses to stopping playing Othello with Honoka until he manages to beat her which, in turn, leads to him being regularly forced to do anything she asks him to do, every time he loses. His relationship to Honoka is very similar to his late sister, possibly that he sees Honoka as his little sister from before.

After losing to Kenichi, he regularly discards his kind personality to those that don't already know about his true nature. Despite refusing to accept Kenichi and the others as his friends, Tanimoto's demeanor has changed considerably since meeting Kenichi and his sister. While still maintaining his cold-attitude, he has become less hostile towards people getting close to him, particularly Honaka. Surprised at how strong Kenichi believes in the ideals of friendship and how they have helped him to come so far as a martial artist have also caused him to have doubts about the path he walks an actually come to Kenichi and his friends' aid, though he always claims he is merely doing it for his own needs such as revenge.

Since his official joining of Yomi, Tanimoto has reached a crossroad in his life; While an unofficial ally of Kenichi, he has intentionally fought each time without killing as a Katsujin Ken believer, while Yomi is a firm believer of Satsujin Ken, meaning he is destined to eventually choose one of the two paths.