Disclaimer: This story contains involuntary castration. Please do not read if you are not interested. The story presented here is purely fictional, any such behavior in real life is completely fucked up.
I was still in high school when my dad remarried a woman who had a daughter, Rachel. She was my age and it was extremely difficult to live with a hot girl you are not related to. It only got harder when her equally hot friend, Lola, started to come over all the time. First it's just minor stuff, like seeing them in bikinis around the pool, or walking around wrapped in their towels after taking a shower. Then one afternoon I stumbled upon something huge.
At this point we were all 18 years old and had been living together for 3 years. In a way I was already used to constantly having two hotties around. But nothing prepared me for what I was about to see. I was home early that day and went to the backyard to relax a little by the pool. That was when I saw Rachel and Lola making out in a tight embrace in the water. They were so lost in each other that they didn't even notice me so I quickly ran back inside.
Once I was in my room I tried to assess the situation. "My stepsister is getting busy with her hot friend in the pool. Plus, our parents are out of town for a few days. How far are they going to go if I don't tell them that I saw them? Maybe I could spy on them a little tonight and hopefully I'll get to see even more." I decided that this was a great idea and all I had to was pass some time. That wasn't too hard as I was obviously in the mood to jerk off after seeing two hot girls making out in the water. It's not like this was my first time fantasizing about them anyways.
I grabbed my dick and closed my eyes. A beautiful scene started to unfold in my head. Rachel was leading Lola into her bedroom by the hand. They are giggling and prancing around as they slowly undressed each other. My stepsister was a stunning girl with a cute ass, slender body, long dark hair and a gorgeous smile. She was a very playful person, always cracking a joke or laughing at something. Lola was equally fun and pretty. A petite girl with red velvet hair and green eyes. Next, they were making out on the bed, naked, their hands roaming all over each other's bodies. I must have been really horny because I came in a few minutes just by imagining them like that. I couldn't wait to see if something like this actually happens.
Evening came and once I didn't hear them laugh or talk anymore I finally left my room. I wasn't sure if they knew I was home but I figured I had better chances if I tried to remain hidden for the time being. As I walked up to Rachel's room I heard moaning from inside. I peered through the keyhole and almost fell backwards. Lola was lying on the bed while Rachel was sitting between her legs, seemingly fingering her girlfriend's pussy. Then after a while she lowered her head and started to eat her pussy.
This was now too much for me. I had to jerk off again. I carefully slid down my shorts and started to masturbate while looking through the keyhole. Lola was moaning loudly at this point and after a few minutes I could see her arch her back as she came. Rachel then slid up beside her and gave her a kiss. The sight was so hot I almost came right there. In fact, I had to let go of my dick so fast, I accidentally hit the door. The last thing I saw through the hole was them looking up with a shocked expression on their faces. I tried to run but my shorts were still around my ankles. I stumbled and fell backwards. The door suddenly opened, two naked girls came out and looked down at me with disgust in their eyes. Rachel, who had her phone with her, took a few pictures of me, half-naked on the floor in front of her room.
"I can't believe you are spying on us, you creep. I always knew your were a fucking perv, but I thought you would grow out of it once you become an adult." As Rachel said this she sounded just as disappointed as angry.
"This is unacceptable." Lola added then turned to Rachel. "We better show these to your parents, Rach."
"No, please. I do anything you want just please don't show these to anyone. I'm sorry I spied on you, it won't happen again."
Rachel and Lola looked at each other for a moment, nodded, then turned back to me.
"Do you agree to be our guinea pig for an experiment tonight? If you do, we'll delete the photos."
"Yes, yes I do, just please get rid of them. No one can ever know."
"Fair enough. Follow us then."
It only hit me after a few minutes that they must want to have sex with me. "What else do they need an adult human male as a 'guinea pig' for? These little rug munchers clearly want to try having sex with a man." I thought to myself.
We went back to her room and they told me to follow all of their orders. I was told to take off my clothes and sit down in Rachel's chair. Lola meanwhile left the room as my stepsister tied my arms and legs to the chair. I gave her a flirty smile and she smiled back at me. But behind that smile her expression seemed sad and disappointed.
In a few minutes Lola was back with a meat tenderizer. She handed it to Rachel who then started to speak to me.
"Listen up, bro. We are sick and tired of your dirty behavior. Do you think we never caught you staring at us while we ere sunbathing? Or always walking by the bathroom as we were inside? Like I said, we knew you were a perv for all these years but we wanted to give you a second chance. Unfortunately, you failed." She sounded both angry and disgusted. I felt so humiliated by everything she said, especially tied to a chair all naked.
"W-what are you talking about, I-I didn't mean to..."
"Shut up. It is time we finally put an end to this. Lola and I love each other, we can't have you creeping around every time we want to be intimate. We decided to get rid of your balls. Without them you will be able to concentrate on something else besides being a pathetic creep for a change."
"No, Rachel, what do you mean, I don't, are you...?" I tried to reason with her but I was shocked at what she just said. Especially since she had that meat tenderizer in her hand. I could barely speak, I was so scared.
Rachel reached down and moved my balls forward so they were resting on the edge of the chair, then she put my cock on to the side, out of the way. I was still trying to beg for mercy but to no avail. She raised the meat tenderizer then struck down on my nuts. It hurt like hell and I began to scream. She didn't care though and struck down a second and finally a third time. After the last strike all there was left of my balls was a bloody pulp.
"Much better now. Don't worry, we won't show those photos to anyone, just like we promised." Rachel said all of this with a happy smile, while I was crying and shaking.
They then drove me to a small clinic. To my surprise, the only one there was Rachel's aunt. It turned out she was a surgeon and was asked by the girls to come as they needed help with me. She removed what was left of my balls and gave me medication. She then explained that both she and her sister - my stepmom - were aware of my nasty habits of spying on the girls and jerking off all the time. They actually wanted to neuter me a long time ago, but Rachel convinced them to wait and see if I can eventually grow out of it.
I never told anyone what happened. I sometimes pretend that I'm still into girls not to raise suspicion. But in reality I don't care about them anymore. I lost all interest in sex after my castration. Nowadays I focus more on school and chores as a good eunuch should.