You Kamiyama, upbeat and sociable, harbors a small obsession with his younger brother, Yuu. His tendency to shadow his sibling has earned him the endearing moniker "Hiyo," as he clings to Yuu like a baby chick. In contrast, Komiya, Yuu's closest friend, possesses a mild complex for his own younger brother, Mayuki.
For the time being, Hiyo and Komiya are content with their current roles, but everything changes when Yuu and Mayuki announce that they are seeing each other. Terrified of being left behind, the two hatch a plan to feign a romantic relationship in order to maintain their brothers' focus. However, even the best intentions can go awry. When the moment of truth arrives, will Hiyo and Komiya call off their pretend relationship?