Ichiko and Otoya have been married for seven years, but unknown to others around them, they are in a sexless marriage, have no children and share a secret: every month, they have an agreement to let Otoya spend the night with his lover.

Ichiko and Otoya have been married for seven years, but unknown to others around them, they are in a sexless marriage, have no children and share a secret: every month, they have an agreement to let Otoya spend the night with his lover.