The boy was thick and long, and I gasped as he pushed in deep. I could have twisted away, run back, but as he filled me I just stood there. His thrusts started to lift me up, and something about the reflection changed. It still showed identical twins having sex, but the longer I stared, the more it seemed like two of me. My brother came with a sudden jet and we both cried out in unison, identical voices and bodies. I felt some confusion - I knew this was one of my brothers, but I also remembered everything that had happened with Runt. And as soon as I thought of his name, the demon appeared next to us.
"So, already tired of being the high school jock?" Runt chuckled and looked me up and down as my oblivious brother hugged me from behind and slowly withdrew, panting. "Different magic here. I can probably change you back most of the way if you want, but something is going to be left as a reminder. Watch out for any other mirrors. The more you get changed by outside magic, the less I can help you later."
My brother took my hand and tugged me back towards the hall. I felt lighter, more nimble, but less strong. It was strange - the difference just a few years made was pretty amazing. He headed for the entrance, but then stopped in front of another mirror. This one was even stranger, showing only one of us. It took me a moment to realize that the reflection's cock was even larger than ours were. And I knew that this mirror would make one of us the others cock!
Runt had followed us. "Interesting! But really tricky. If you become the cock, his essence will be dominant. If you become the boy, your essence will be dominant. In either case, separating you will be very difficult.