Tatsumi Kiyosu is the twelve-year-old younger brother of Ryūji Kiyosu, born three years after Ryūji and three years before his younger sister Miyu in their family of five siblings.

He possesses purple eyes and dark gray hair featuring blue highlights, with a visible bandage on his right cheek. His typical outfit is a black-and-white tracksuit layered over a white shirt, completed by dark blue and grey sneakers. When piloting his Shinkalion, he dons a specialized suit resembling his brother's, though modified with additional vest and pants elements.

Tatsumi exhibits an impulsive and headstrong personality, frequently overlooking details and acting in ways that draw reprimands from Ryūji. Despite this, he shares his brother's dedication to karate and a strong commitment to family, allowing them to maintain a generally positive relationship despite occasional friction. Compared to Ryūji's initial reserve, Tatsumi displays a more open and casual demeanor with fellow Shinkalion drivers. Beyond combat and martial arts, he shows notable enthusiasm for eating, often consuming large quantities of food rapidly, which surprises those around him.

He serves as the pilot of the Shinkalion N700A Nozomi, first appearing in Episode 25 of the first season, participating in battles against threats alongside other drivers. Tatsumi's character dynamic with Ryūji establishes a recurring pattern later mirrored in *Shinkalion Z* through the Anjou brothers: Nagara Anjou shares Tatsumi's position as a younger brother pilot with similar martial arts skills and impulsive tendencies, while Shimakaze Anjou assumes a role comparable to Ryūji as the older brother who initially piloted the predecessor N700-series Shinkalion before transferring it to his sibling.

Tatsumi Kiyosu does not appear in the third season, *Shinkalion: Change the World*, which features a new cast and separate storyline.