I was at my girlfriend’s place to surprise her sister with a party for her birthday. I (24M) have been friends with the elder sister of the family for about 5 months before I started dating the younger sister. However, I ended up dating the younger sister but I always felt something was missing. On the day, she and I started talking about past and how close we used to be. One thing led to another we caught ourselves flirting with each other. Two minutes later I’m making out with her in the toilet. I pushed her against the wall and held her hands over her head. I felt my entire being saying ‘this is wrong’ but that only made things worse. I was touching her face, neck, breasts hips and finally worked my hand down to her skirt. I knew I shouldn’t but I couldn’t resist. I touched her panties and the were so wet. I smelled my fingers, looked straight in to her eyes and slowly pulled her panty to the side. I felt her regrowing pubic hair and the engorged slimy pussy. I slid my fingers in and she was gonna moan so I kissed her again while putting the second finger in. After about 2 mins I felt her insides getting tight and felt her cumming. I licked my fingers and we both walked out in a haze. She was staring at me like she wants me to fuck her all night but we haven’t spoken since then. I went home with my fingers smelling like her pussy. It still feels wrong but my cock gets hard everytime I think of it. (Not real Scenario based on real life incidents)