I (24m at the time) slept with my girlfriends sister (18f at the time)

This happened 10 or 11 years ago. I we were at her 18th birthday party (small family gathering) and she mentioned that she was not doing well in math. My girlfriend mentioned thay I was good at math and that I could tutor her after-school a few times a week.

So for a month we studied a couple times a week and got to know each other and found out we had a lot in common. At the end of our month or studying she had a test and did really well (think 50 student got a 70ish score) and she was really happy. When we got together for her next study session she was really excited and showed me her score. We hugged each other and she kissed me. I kissed her back but then we stopped and realized what we did and said we can’t do this and after a few awkward minutes went back to studying.

We studied for a few more months without incident. We did start hanging out after studying and texting each other. We scheduled a study session on a Saturday and she came and picked me up and went back to her house. We sat in the dining room and she sat on the same side of the table as me. We were going over assignments, tests, and quizzes and focused on the areas that she was getting wrong. Her final exams were coming up and she needed to pass her math exam (60ish mark) in order to have enough credits to graduate. So we studied for a few hours that Saturday and then she put her hand on my leg and slid it up and over to my cock. I didn’t move and just looked at her and was like what are you doing. She’s now rubbing my cock and said she wanted to repay me for all my help getting her ready for her final. She unbuttoned my pants and pulled down my zipper and fished around and pulled my cock out and started stroking it. She then got on her knees and started sucking my cock. I didn’t stop her and even put my hands on her head and went along with it. I came in her mouth (she swallowed) and then I did up my pants again and hung out for another hour norhing else happened that day but she had the biggest smile. When she took me home I asked if she needed another study session before her final next week and she said no.

I texted her the day of her final and told her good luck she said thanks and I didn’t hear anything from her. A few days later I get a text from her to see if I was home. I told her that my gf just went to work and I was finishing up supper but I was home. She said ok and she was coming over in a bit. An hour.latwr she arrived at my house and came in and sat on the couch beside me and told me that she passed her final and she was going to graduate. She was so happy and we started to hug and she kissed me I didn’t pull back this time and started kissing her back. She shifted herself from off the couch and onto my lap and kept kissing me. She stopped kissing me and said she wanted to thank me because without my help she wouldn’t have passed her final and been able to graduate and with that she took off her top and bra. I started to suck on her nipples and she reached down and pulled my shirt off me. I pushed her off me onto the couch and took her pants and panties off and started eating her pussy. She came pretty quickly from my tongue. I then got up and pulled my pants and boxers down and she jumped off the couch and knelt infront of me and started sucking my cock. I pushed her back onto the couch and climbed on top of her and started missionary but the couch just wasn’t wide enough so I flipped her over and tried doggy style. I grabbed her hips and slide into her and after a couple pumps figured that was not working either. Finally I decided that the couch wasn’t going to work and went to my bed. I climbed in the bed first and got her climb on top of me and slide my cock inside her. She rode me until we both came and then we layed in the bed for a little while afterwards.

That was the last time we did anything else. We still text and see each other at family events and I keep thinking about that night when I jerk off.

Source: reddit.com/r/eroticliterature/comments/nq9brq/i_24m_at_the_time_slept_with_my_girlfriends