Chikan densha: Kuikomu nama-shitagi

Summary

On a crowded train, an office lady, Rika, is attacked. When Rika turns around, she lets out a cry of shock. The man is Tatsuo, who is married to Rika's co-worker, Miho. Later, Rika visits Miho's house and confesses what Tatsuo did to her, but...