Shuuchizuma Chijoku Densha ~M no Kakusei ni Tomadoi Ochiru Kouhai no Ane-san Nyoubou~

Reika, a 29-year-old housewife, feels her six-year marriage growing stale as her husband shows no interest in sex. Doubting her own attractiveness, she encounters Keiji Joujima, a 30-year-old serial molester who preys on women in trains. Under his assault, Reika discovers her hidden masochistic and exhibitionist tendencies, leading her into a world of shame and temptation. This story follows her reluctant descent into M awakening.