This... is a fairly simple idea, which can be done in many different variations. If any of these appeal to you or the idea of romance or an affair that turns into a romance is one you like, PM me and we can work something out.
I want a story filled with romance.
Some ideas are:
1.) Lovers that were separated. Perhaps circumstances did not allow them to be together at a certain point and now they've met again and the male in the relationship is determined to make her his.
2.) A girl dating the wrong sibling. She's dating one brother, but in love with another. What happens when one night they give into their feelings?
3) A woman has been hurt by men in her past. She meets the quintessential playboy who decides that he must have her. But, what happens when he decides he wants her for the keeping?