Age gap/underage m/f in a postapocalyptic or otherwise isolated setting. An older guy and younger girl basically only have each other for company, and get over the taboo of their age difference because they literally only have each other. A sexual relationship that's not necessarily born out of love but mainly because they have nobody else and it's a stress relief.

I'd like the relationship to be similar to Joel/Ellie, or hell just Joel/Ellie as characters. I have a preference for the younger party. Drop a sock!