My girlfriend is on her period so she doesn't let me touch her. She promised to make love with me next week. I tried to endure until then. When I got home, I saw a naked person, a very attractive body. I thought it was my girlfriend so I rushed in without much thought. After a while, I realized it was my girlfriend's sister! I regret and apologize to her, but it seems she's not angry with me. Instead, she wants to extract my sperm...