Minami and Otome have been step siblings for five years. Their grandmother is staying with them, taking up Minami's room while she recovers from surgery. This results in Minami having to bunk in his sister's room. They have divided the room with a sheet hanging from the ceiling between the bed where Otome sleeps and a futon on the floor where Minami is sleeping. This often results in Otome either falling half-dressed out of her bed and onto Minami or Minami knocking down the sheet while Otome isn't there and rifling through her things. Shortly afterterwards, a boy named Amane kisses Otome and they begin to date. This sparks emotions in Minami, forcing him to realize that he may feel more for Otome than brotherly love. As Minami begins to express this inner struggle through teasing, harsh words, and awkward romantic gestures, Otome comes to feel the same things.