Inseparable

Brad held the newspaper up close to his face, concentrating on reading and trying his best to ignore the growing cries of his girlfriend, Kim, from his sister, Allison, eating her out beneath the table. This was the new normal after the visit from The Stranger.
He’d blown into the house and, with a wave of his hand, swapped Kim and Allison into each other’s bodies. Then with another wave he’d linked their minds, giving Allison a voracious need to eat her own pussy whenever Kim got the least bit horny.
From then on the two were inseparable. Literally, most of the time. At the slightest inkling of desire from Kim, Allison dove between her former legs, using her tongue and fingers to urge soft moans from her former lips. Allison teased her former clit until it budded out beneath her tongue and her new cheeks and chin grew slippery with her own juices. She wouldn’t stop until Kim climaxed around her face, crying out as her new body was racked with orgasm.
After Allison made Kim cum, she crawled back up and resumed her place at the table to finish her breakfast as though nothing had happened. They didn’t talk about it anymore and it had become so regular that they hardly had any shame. It was just a fact of life.
Brad missed his girlfriend but could no longer be with her. The instant he kindled any sort of desire within her, Allison would barrel into the room from wherever she’d been and thrust her face between her former creamy thighs, lapping eagerly until Kim’s body exploded around her in a shuddering orgasm.

A mean-spirited sorority girl is possessed by an occubus, a demon that takes over a person and thrives on their sexual energy, its demonic male essence gradually turning her body masculine while she remains helpless inside in Occubus, available on Body Swap Stories or Smashwords. Preview here.