Natsume Aihara, at sixteen years old, has never explored dating or relationships. She attributes her lack of experience to the restrictive influence of her overbearing neighbor and older brother figure, Sousuke Mikami. Despite the significant age gap between them, Sousuke has remained a constant presence in Natsume's life, going so far as to work at her high school to keep her under watchful eyes. While Natsume used to look up to him, she has grown to recognize that his behavior towards her has become unnervingly obsessive and twisted. As a result, she resolves to pursue a relationship with someone her own age, yet can't shake off the unconventional emotions she continues to harbor for Sousuke, who knows her inside out.
