Haruka, an adviser to the badminton club, had an affair with her colleague Ishida. Although she started dating without knowing that the other person had a family, the relationship still continued even after knowing that Haruka had become a convenient woman. At one point, her student Yoshii witnessed this 'relationship between two people who should not be known to anyone'. Yoshii finds out that Haruka, who she loves, is having an affair, and uses it as a material to force Haruka into having a physical relationship with her.
