Naoto Watari has had his share of struggles: his parents died two years ago, and now he and his sister live at his aunt’s house. There, his desire to protect his sister earned him notoriety as “the guy with the sister complex”—which never mattered to him, as his sister always came first. But when Satsuki, a childhood friend-turned-enemy(?), becomes his school mate, Naoto’s ordinary life is thrown into chaos … and Satsuki may just be the beginning.
Naoto musters up all his courage and confesses to Satsuki, proclaiming that he wants to form a family with her. However, the two are busy working and studying for the sake of their future, so they don’t have much time to see each other. And so, Naoto persuades his aunt to let him live with Satsuki during summer break!