As high school girls Aya, Yuki, and Yuri ride a crowded train home, a skilled older man takes advantage of their innocence. He discreetly seduces them one by one, escalating from teasing touches to explicit acts of submission. Each girl surrenders to hidden desires, their flushed faces and soft sighs betraying newfound pleasure as the train jostles them through a journey of secret, forbidden climaxes.