Tony had been having a secret affair with Lisa, his sister's best friend, ever since they swapped bodies in a science experiment gone wrong. They didn't want to complicate things any more than they already were, but they both couldn't hide their feelings for each other, brought about while helping each other adjust to their new bodies.
They tried to resume their old lives but found it difficult to go back to work without being gawked at, or pointed at on the streets. It had made the news and everyone knew they'd swapped bodies. Tony had stopped talking to a lot of his friends after their attitude towards him changed and they'd repeatedly asked to cop a feel.
Tony and Lisa took comfort in each other. And the comfort led to love, and the love led to sex. Tony grew to enjoy spreading his legs for his former body and playing with his tiny breasts, as Lisa slipped her tongue up against her former folds and brought him to orgasm, knowing exactly how to please her old body.
It was during one of these afternoon trysts that Tony heard his sister coming home. His eyes flicked to the door but, unfortunately, he couldn't get Lisa to stop in time, and the orgasm hit him as she walked in through the door. Tony's jaw dropped open and he moaned and shook as Lisa's tongue found his sweet spot, sending a joyful orgasm through him.
After that it was no use trying to keep their relationship a secret. Tony's sister may not have liked it, but then, it wasn't her choice.
A demon continues his plan of body possession and body swapping to grow his powers in The Devil You Know (Part 2), available on Smashwords or Amazon. Preview here.