The Mikadono sisters—Miwa, Niko, and Kazuki—stand at the pinnacle of Saika Academy as its Three Royals, renowned respectively as prodigies in shogi, karate, and theater. Unfortunately, they have drifted apart from each other due to their overwhelming dedication to their fields, effectively turning them into strangers living under the same roof.

Enter Yuu Ayase, the son of the late Subaru Ayase, a legendary actress who graduated from Saika. Unlike his mother, Yuu lacks any extraordinary talent whatsoever, much to the disappointment of those who knew her. Still, he transfers to her alma mater with one quiet promise in his heart: to fulfill her final wish that he build a true and happy family.

It just so happens that the Mikadono patriarch is also Subaru's longtime friend and benefactor, and he offers Yuu both a place to stay and a fresh start. Thrust into the lives of three estranged sisters who act cold toward him, Yuu may not be a genius himself, but the clumsy sincerity he brings might be what they all need to start anew.