And in my opinion, more than just serving the narrative, leaving in the nuances and awkwardities of sex makes it more appealing even if all you're looking for is something to get off to. It adds dynamic and charm to the encounter, gives you more thoughts and ideas to explore, etc. Because humans aren't perfect and sex is done by humans, then sex shouldn't be, either. It should have ups, downs.
Prism has, so far, the best depiction of awkward first time teenage sex I've seen.
Hanjuku Joshi is a close second, though.