Iroha's husband passed away two years ago. Her daughter, who had left home to get a job, decided to move in with her husband when she got married, and the three of them lived together. One day, Iroha peeked at her son-in-law masturbating. She was shocked, but thought it was normal for a young man. Then one day, when she was alone with her son-in-law, she listened to his worries about his nighttime relationship with his daughter. The two of them, who had been peeking at each other's masturbation, ended up laying together, despite the excuse that they were just rubbing their hands as an experiment...