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

Hikaru and his younger sister have lived together supporting each other. When his younger sister finds someone important to him, he decides to leave home, but he is held back and now lives happily with his sister and her husband. One day, after working overtime, I fell asleep due to the shaking of the train. When I woke up hearing heavy breathing, I found my sister's husband jerking off his cock while peeking inside her upturned skirt...