Adam and Mark found the spellbook in the library, but not just any spellbook, the Tantrus Libidica. The spells all seemed pretty simple and powerful, but required fuel. Fortunately they were both young men in their early twenties, and the Tantrus Libidica was a sex magic book. Some sperm was all that was needed.
A few weeks of collecting and they each had a jar full. More than enough for the spell they wanted to cast. To summon a big titted horny babe they could screw all the time. Adam read the spell, holding the two jars in his hands.
There was a flash of light and a puff of smoke where Adam was standing. When the smoke cleared Adam was still there, only he was holding two massive tits in a lace teddy instead.
As Adam stood their dumbstruck, Mark leafed through the Tantrus Libidica to see what went wrong. He found it a few minutes later. The spell to conjure a woman needed twenty jars of semen, not two. Then he looked up the spell to turn Adam back. They’d need at least three jars, and now they only had one person capable of contributing…
Adam played with his new boobs and smiled, feeling a warm empty feeling in his new crotch. Adam promised to help out any way he could. When Mark asked how, Adam jumped on top of him.
The weeks went by but their rate of collection was pretty slow. Adam almost always held Mark pretty tight when they fooled around, and so most of Mark’s cum ended up on or in Adam. Adam didn’t mind at all.