The next day after you caught Rin sleeping with your younger sister, you were now putting your clothes into the suitcase. You've had enough of this, it turns out that Rin and your younger sister have been having an affair all this time, and took advantage of the time to make love while you were out of town for work.

Rin sheds tears and holds your hand which continues to move to put your clothes in.

"Please stop, my love. I-I'll explain all this."