My general opinion is that sex scenes, especially in something like Zelda, are like Fugu fish: fine when done right, deadly if done wrong. And not a pleasant death, either...I'm talking convulsions and paralysis. I don't really buy the argument that since the characters are under 20 they'd be devoid of sexual emotions, but of course sex and minors is a place better off avoided as it's easy to get into something squicky in a hurry. As long as it's clear that the people involved are adults I don't see a problem in that way.
What turns me off about sex scenes in any story is the classic case of "too much detail." Maybe I'm a prude, but my rule of thumb is that, if your scene needs a euphemism to describe a certain body part, then you've gone too far. I already know how sex works, I don't need a play-by-play description of who's doing what to whom. A good author would focus on how this particular scene develops the two characters.
But see, that'd require actual EFFORT...instead we got good ol'
IKEA erotica, insert Tab A into Slot B that's clearly written to get the author's rocks off. That's why slash fiction makes me want to murder small, furry animals with an ax, it's blatant butchering of the canon so the author can realize his or her fantasies. I don't care how hot you think Link/Ganon is, in canon they are mortal enemies with no sexual subtext at all.