Ah... so this is one of those weird ones that's like a perfectly normal, even pretty decent story—except gay sex just shows up, bam!, out of nowhere, and with no explanation, sandwiched between otherwise-normally-developing human interactions between the characters, and no one really seems to think it's a big deal.
(But, in this particular case, if you can ignore that WTF-ness, there's actually a relatively nice story here, I think.)