Tatsuya is the main protagonist of the series. Both his parents died in a car crash prior to the first chapter of the manga. Tatsuya wants to be a "man of high caliber" as his dying father said with his last dying breath.Because of that goal, he met Seine Miyazaki in the first chapter, and tried to save her from a bully, although Seine didn't want that. Tatsuya lives with cousins in his manison (because of his parents death) but his cousins only want his inheritance. When Tatsuya discovers that Seine lives in a cardboard box in the park, he invites her to live with him.