To support her father-in-law who was left alone after her mother-in-law passed away, Rika moved into her husband's family home. Her husband is a germaphobe and overly serious; despite the father-in-law's pleas for grandchildren, the couple has no sex at all, leaving Rika feeling lonely. One night, while lost in her loneliness, she is caught masturbating by her father-in-law. The next day, as soon as her husband leaves for work, her father-in-law pushes her down. She knows she shouldn't cross the line... but her body gradually begins to crave him...