Yumi is set to introduce her fiancé Shigeru and his younger sister Kiyoko to her stepfather, Tokujii, with whom she has lived for many years. Upon hearing news of his stepdaughter's engagement for the first time in a while, Tokujii wears a gently affectionate smile. Seeing this, Yumi finally begins to feel at ease. However, she suddenly notices Tokujii glancing intently beneath Kiyoko's skirt. Witnessing her stepfather, who had never shown interest in women before, now clearly drawn to Kiyoko, stirs a deep unease within Yumi. This tangled mix of emotions foreshadows the beginning of a new, forbidden relationship.