Joe was terribly jealous of the way his girlfriend would writhe and moan on her favorite toy. They have sex, and she'd writhe and moan then too, but it never seemed as earnest or powerful.
One day he told her he couldn't take it anymore. He couldn't understand how she'd want the machine when she had him. She had to pick. Him, or it.
His girlfriend thought Joe was overreacting. He just didn't understand. Sex was fun and all, but her toy - the machine - it was indescribable. Of all the vices and things she could be addicted to, the machine seemed like a pretty tame one.
Fortunately, she had a book left behind by her great-aunt. She'd only flipped through it a few times, but knew there was one spell in particular that could clarify everything for Joe.
Joe was pretty shocked to find himself a woman, but also admitted it was kind of cool. He liked playing with his own tits and he told his girlfriend he'd be happy to try a little lesbian experimentation with her.
She agreed, but only if Joe tried the machine first. Joe sensed her play here, but decided he could tolerate the machine a little longer if it meant trying lesbian sex.
Only when he squatted down on it, Joe started moaning like a whore and his legs went numb. He shuddered and shook and gasped and seemed to cum almost continuously. He had no idea anything could feel so good.
They did have their lesbian sex, but only while one of them was riding the machine.
Afterwards Joe told his girlfriend she could keep the machine, but only if she kept him as a woman too.
The machine saw twice as much use after that.