This can be M/F, F/F, or even Futa/F, if you like.
Alright, so we know that in the X-men world, there are mutants with powers, and normal humans.
Now, we also know that there are certain humans who are...strongly Anti-mutant.
Now, what I'd like this story to be about is a Young man/woman who discovers they have mutant abilities, and has actually been hiding/repressing them. Sure, they experiment a little with them, but never in public, because of one reason...their best friend, and largest crush, is a woman who is very much against mutants, drawing him/her into their hate speech and other things of that nature.
Now what happens when he/she reveals their true feelings....and what they really are?
Now, of course, the Anti-mutant character will also have strong feelings for the mutant character, strong enough that one could call it love...but will that over-ride her hate/fear of mutants? D:>
So yeah..that's the idea, folks.