"You look Time Lord."

Not... really? Asexuals can be in love with someone, in a romantic sense, and still not want to have sex with them. For a romantic asexual, there's an intermediary step that might well be filled with, say, kissing, sharing a bed and general physical closeness without any kind of arousal factoring in.

I'm possibly not explaining this very well because, being ace myself, it makes far more intuitive sense to me than the sex does. If that's the case then I apologise: keep asking me questions if you want and I'll do my best to make this make sense :) You might also want to check out the FAQ I linked to upthread (here it is again), because the folks at AVEN are far better at this than I am.

EDIT: Sorry, just reread: in terms of fic, I guess there's not much difference between this and a PG-13 romance? Except in terms of implication: when I write PG-13 'normal' romance, there's usually at least some implication that they're getting busy offscreen. When I write ace romance, they're not.