Human Sexuality Class Week 6 - Sexual Intercourse [Multiple M20's/Multiple F20's] [Public Sex] [Different Positions] [Sister-In-Law]

Links to the previous weeks' stories [here](https://www.reddit.com/user/sneberd/comments/1k9tquh/my_stories/).

# Week Six - Sexual Intercourse

When we got to class for week six, nearly everyone was naked already and it was really quite a sight to behold. By the time Kate walked in we had disrobed as well, and Kate soon joined us (“It’s always more fun being naked!”). Other than some hints here and there, we had not been told beforehand what the course itinerary would be, so we were all on edge about tonight’s topic. “Tonight,” Kate started, “we will finally get down to proper sexual intercourse!” I felt a thrill go down my spine. While Becky (my sister-in-law) and I had gotten very close during the last five weeks, my penis had never actually been inside her vagina, and I felt like that was an important distinction. My wife Jessica (Becky’s sister) had been supportive so far of our class experience, however I didn’t know how she would feel about us having actual intercourse. As usual, however, my primary thought process was occupied by the blood rushing to my hard cock, so I pushed any reservations out of my mind.

Kate spent some time talking about protection (we had touched on the subject briefly in the first week’s introduction class, but never with actual demonstrations) and showed the class (using first a cucumber and then my penis) how to apply a condom. She then paired the class up (using more cucumbers where there were extra girls) and had everyone practice applying a condom on themselves (for the guys) and then their partners (for the girls).

Becky slowly rolled one onto my cock, which felt very erotic, but then proceeded to unroll it, whispering, “if I’m going to put that inside of me, I don’t want anything between us, any objections? I’m clean…” At that point I really would have done anything she asked me to do, but I didn’t have any problems fucking her raw, neither of us were promiscuous.

Kate noticed this interaction, and confirmed that we would indeed be having vaginal sex that day, and confirmed that we wanted to proceed without a condom. She then asked about where I wanted to cum. “Inside of me,” Becky said, somewhat breathlessly. “I’m on birth control. I want his cum inside of me.”

I almost came right then on her arm, but managed to contain myself. “If that’s what you two want, that’s fine with me,” Kate said, “but just make sure you hold off long enough to go over some basic positions. Let’s start with missionary.” She led Becky over to the bed and had her lie down on her back. Becky was breathing heavily and had her eyes closed. Kate then directed me to lie down on top of her and insert my penis into her vagina. I placed the tip of my cock against the edge of her pussy and could feel how wet she was. I slid it up and down a couple of times, and then pushed inside of her. The feeling was incredible; she was tighter than my wife, and I felt the most amazing squeezing sensation against my cock as I slowly slid it into Becky’s cunt.

“Ohhhhh fuuuuuuck” Becky moaned as I entered her, “you’re so big. I’ve never felt this full before, what a sensation.”

I had never had sex in front of other people before, but it had always been a desire of mine, and it did not disappoint. Knowing that 20 other people were watching us added a level of erotic-ness that made it feel more amazing than ever; that and the fact that it was with my sister-in-law, who I had dreamed about fucking for years. I wanted to fuck her hard and fast, but knew I wouldn’t last long if I did, so I gave it a couple of long slow strokes, and then pulled out. We were both breathing heavily, and it seemed that the rest of the class was too.

Kate then had Becky turn over and rest on her hands and knees, facing the class. She then had me climb up behind her and enter her doggy-style, which is probably my favorite position, and I reached around and held her breasts, which were hanging down in front of the class. Again I really had to guard myself to keep from cumming, and tried really hard to focus on Kate’s ongoing dialog with the class - she was talking about how this was the best position for pregnancy, if desired, due to the downward angle of the vagina. She had us rotate 90 degrees so the class could see my penis coming in and out of Becky’s vagina, but stopped us before much longer.

We next did a position where Becky was laying on the edge of the bed and I was standing up, her feet on my shoulders, and I loved the angle of being able to see her face and breasts while we fucked. Kate then had Becky put her legs around my middle, and had me pick her up while still inside her, my hands under her ass. This was also something that I had never experienced before, and found it easy to lift Becky’s small frame. There was a smooth part of the wall, and I pushed Becky up against it and held her there, fucking her standing up.

I felt very much on-the-edge, because as soon as we would get going, Kate would have us stop and direct us into a different position. Like me, I think Becky was also building tension, “Just two more positions,” Kate said, seeming to read our thoughts, and you can cum.

She then directed me onto the bed and had me lie on my back, my feet towards the class. “We are going to demonstrate reverse cowgirl position, and then finally cowgirl position.” My penis, when hard, had always pointed more upwards than outwards, and reverse cowgirl position had never been something that I felt had worked well. But with Kate’s direction, and with the knowledge that the whole class could very clearly see my penis inside Becky’s vagina, we seemed to make it work OK. Kate had Becky do most of the work, angling herself so her back was almost onto my belly, and watching my cock to make sure it didn’t fully come out of her pussy. The feeling was amazing as Becky slid her body up and down mine, my cock coming out of her pussy almost all the way before going back in.

Finally, Kate had Becky turn around and face me, me on my back and her sitting on my cock. “This position can provide some of the most stimulation for the female, and most ladies are able to cum in this position faster than any others,” Kate directed the class. It felt amazing for me too. I first placed my hands on Becky’s hips, guiding her back and forth on my cock. She leaned down and I put a breast in my mouth, sucking gently on her nipple, and then the other one. She leaned back again, and I put my hands on her breasts, kneading them and feeling her nipples pinch between my fingers.

Becky was really getting into it, and started moaning loudly, and I found myself moaning with her. I remembered back to the previous week when Kate was talking about being one with your partner. I wanted to cum with Becky, so I listened to her body, and her moaning. I knew she was getting close, and I was too. I put my hands around her hips and onto the cheeks of her ass, and pushed and pulled with her movements, as she rocked back and forth on my cock. Before long she screamed with orgasm, and I felt her whole body shudder with it. I came too, in what felt like the most powerful orgasm of my life, as I filled her tight cunt with rope after rope of my seed.

The whole class had been watching us silently, everyone naked now and many of the observers touching themselves. After a moment, Kate instructed them that, if desired, they could team up and practice some of the positions, but to be sure to use protection and be conscientious of their partner’s feelings and desires. She also said that they could switch between different partners if they wanted to, but never more than two individuals could be together at a time (“threesomes and multiple-partner sex will be covered in week nine.”) Kate and I felt spent though, and opted to stay on the bed together naked and cuddle/fondle/make-out a little. That is, until I found myself hard again, and we spent a little bit more perfecting the doggy-style position, and managed to both cum one more time.

As we drove home that day together it felt like perhaps a line had been crossed. I know this was just for a class, but I felt myself developing feelings for Becky, and had the desire to fuck her again, as soon as possible. We talked a little, and although she admitted feeling the same, we decided to cool things down a little, but also to not tell Jessica about the details of our evening just yet. Unfortunately that resolve didn’t last very long…