Post-apocolyptic guy who was denied education, so literally knows nothing of the real world, and since most of humanity is wiped out, he doesn't know much about society, either.
He's off to wander the world with a gay guy looking after him. So even though the boy is truly heterosexual, since he's only seeing guys and hearing the views of a flamboyantly gay guy, he's constantly questioning his identity.
Post Nuclear Fallout. Do it justice.
The plot's actually way more complicated than that, but the summary's good enough. =p