Oh! Maybe I shouldn't have said "features", change it to "contains" :P

So what would you call a fanfic that has same-sex characters that are shown to be together (but aren't in the source), but the story is about a straight couple (which may or may not be together in the source), not their romance but their quest to defeat an Evil Wizard?

Slash/Het/Adventure.

Was that a romance? Was it slash? Of course it was slash, but it wasn't a romance

You can always put 'Other' in the fic category section, I guess?