The Kazama and Etsuko families live in the same apartment building and are close enough to share meals. One evening, Etsuko suggests swapping mothers. Yumi hesitates, but her adult son Takashi and Etsuko’s adult son Riku eagerly agree, leaving her little choice. During spring break, both families confront the reality that Etsuko neglects housework and parenting. Unaware of this, Yumi is consumed by the younger adult Riku’s sexual hunger and his longing for the maternal love he never knew.