In the story of Kodocha, Tsuyoshi is a sweet, nerdy kid, and Akito Hayama’s best friend. He says he likes Akito because Akito never makes fun of him for being a “momma’s boy.” Akito is also the only person who can calm Tsuyoshi down when he flies into a violent rage.
In the beginning of the story, Tsuyoshi has a crush on Sana, which causes a brief rivalry between him and Akito. But Akito fixes him up with classmate Aya, and she and Tsuyoshi turn out to be a perfect couple.
Throughout the story, Tsuyoshi is one of the many characters exasperated at Sana’s obliviousness to Akito’s affections for her. He even TELLS Sana that Akito really likes her, but Sana refuses to believe it unless she hears it from Akito himself.
He has a little sister named Aono whom Sana really likes.
Tsuyoshi and Aya remain a couple throughout the story, as well as good friends of Sana and Akito.