It all started when a drunk Hikari suddenly kissed her husband's brother, with whom she lives. That was the start of an affair that continues in the family, hidden from her husband. However, Hikari is worried that her husband will find out, so she consults her brother-in-law about ending the relationship. However, her Hikari-in-law has recorded their relationship on video, and uses that as an excuse to refuse to end the relationship...