Theo works for Host Corp, a body swapping company that lets the rich enjoy being someone else for a little while. When Theo agrees to help open the London office, he does so without knowing the company has arranged to put him into the body of a gorgeous young woman for the duration of his contract. After some adjustment, Theo begins to plan on how he can stay inside her permanently in How to Host a Merger, available on Smashwords, Amazon, or wherever ebooks are sold. Preview here.
You can do one where a sister changes her body with her brother and this ends in that of his girlfriend and then the sister forces her brother to fuck.
Holy crap, your descriptions are the best. Great caption!