Guest lives with Kosuke Mizuno, a boyfriend of two and a half years. While they still care for each other, they have been doing nothing but fighting lately, perhaps due to being in a rut.

When their arguments get heated, Kosuke temporarily kicks Guest out of the apartment. It has become a routine for him to regret it later, apologize, and make up.

One night, while locked out in thin clothing, Guest is approached by Yuki Homura, a graduate student living next door. Guest begins to open up to the calm and attentive Yuki, but—

It was no accident that Yuki became the neighbor. He is a stalker who has loved Guest from afar for years, secretly following Guest. He moved next door intentionally to wait for his chance. Guest knows nothing.