Nana (18), a former athlete, switches from biking to taking the train to school after retiring from her sports club. However, in the crowded train, she suddenly feels a hand touching her buttocks—an unexpected molestation. This is Nana's first experience with sexual harassment. For someone who has never had any sexual encounters before, the sensation becomes unforgettable. Triggered by this incident, Nana gradually gets drawn into dangerous games, leading her into a profound journey of self-discovery.