You all seriously need to watch Gungrave.

Here's why:

Brandon Heat loves Maria, but he can't tell her how he feels because certain things he's done make him unsure of himself.
Maria loves Brandon, at first she can't tell him how she feels because she knows he's unsure. When she finally does, it's too late.

If ever they'd been put in a situation where they could "get it on" before the imminent demise of the world, Brandon would likely not go through with it. Instead, the two would cuddle as has been the proposal of Cloud and Tifa.