My wife's sister-in-law, who was panting on the last train, noticed my erection and started seducing me.

My older sister Hikaru lives with her younger sister and her husband. Hikaru, who has been close to his sister for a long time, was planning to leave home after getting married so as not to disturb her, but her sister and her husband held her back, and now the three of them are living happily together. One day, perhaps because I was tired from working overtime for days on end, I boarded the last train home and fell asleep right away. When I woke up in a hurry, my sister's husband was in front of me, looking through her skirt and jerking off his erect penis.