WAAA-008 Fucking the wrong lover's sister

My girlfriend is on her period so she won't let me touch her. She promised that next week she would let me make love to her to my heart's content. So I tried to endure until next week. As soon as I entered the house, I saw a nude person with an extremely seductive body. Thinking it was my girlfriend, I rushed into making love without thinking much. But after a while I discovered that it was my girlfriend's younger sister! I regretted it and apologized to her, but it seemed like she wasn't angry at me, but instead, she wanted to squeeze out all my semen...