Homeland: Tokyo, Japan
Weight Class: Junior Lightweight
Height: 171 cm (5'7")
Reach: 171 cm (67")
Style: Out Boxer
Stance: Orthodox Stance
Current Affiliation: Kamogawa Boxing Gym
Ippo's senpai and Aoki's best friend. He is the smooth, collected type and a romantic at heart, but trains as hard as anyone. His style incorporates a fast left and faster footwork. In the past, he and Aoki were the toughest high-school thugs around, but now Tatsuya's real job is at his family's flower shop. He is a junior lightweight boxer. Along with Makunouchi Ippo, Takamura Mamoru, Aoki Masaru, and Itagaki Manabu, he rounds out the core members of the Kamogawa Boxing Gym. His main fights in the series are against Mashiba Ryou and Eleki Battery.
Kimura and Aoki Masaru were best friends since kindergarten. In high school they began brawling and causing trouble with students from rival schools, namely North High, which eventually led to their expulsion. Kimura was the most affected by this because he was worried he had disappointed his mother. One day the pair attacked North High's Takamura Mamoru and lost miserably. Seeing Takamura's strength as a boxer, they decided to join the Kamogawa Boxing Gym to try and become strong too.
Kimura became a delincuent beacuse he was bullied by an older boy, and when his father went to confront the boy's father, he was pressured and ended up apologizing, this made Kimura lose all respect for his father, becoming more violent in both his house and in the outside, and decided to quit highschool without his parents knowing.
Like Aoki, his boxing ability is also downplayed for much of the series (albeit not quite as badly). Despite this, he has proven to be a good boxer with solid all-around ability. Miyata stated that as a boxer, Kimura had no weaknesses (despite also not having any strengths) and Miyata's father said that although he was only ranked third before his fight with Mashiba, his talent surpassed that ranking. Mashiba himself admitted that Kimura was his strongest challenger. He shows strength around the level of a national champion, as he was able to draw with Eleki Battery twice and only barely lost to Mashiba.
As fast outboxer, Kimura is often asked to be a sparring partner for as Makunouchi and one time for Miyata, though Kimura benefited more from Miyata's sparring.