While working on his manga in the library one day, Naoto Hachiouji encounters Hayase Nagatoro, a first-year student who relentlessly teases him every day. She chooses to play with him from that point on after reading his story and observing his awkward demeanor; she even refers to him as "Senpai" rather than by his real name. At first, Nagatoro's incessant pranks are more annoying than anything and make him feel humiliated because he is compelled to indulge her whims. However, as their relationship grows, a peculiar kind of friendship forms, and Naoto discovers that living with Nagatoro can actually be enjoyable. But one thing is certain: His days will never again be monotonous.