Yuko Yajima works at a library To her coworkers she appears as an extremely shy and introverted person who hardly lets anyone know her true feelings and never smiles However her interest in a man living in room 202 Mamoru Kosino leads Yuko into some risque behavior The interest turns into obsession as Yukos jealousy turns into a thrilling game where she sneaks into apartments and scares tenants away hoping to have Mamoru all to herself