And once again you've managed to come up with something pretty original. The only story I know with insertions of this relative size is 'Dark Castle' by sickbasterd on hentai-foundry, which was linked to from some thread here a few months ago. I enjoyed the novelty of that, though the girls' dying was of course a bit of a shame, so I'm very happy to see one where the girl stays alive, and fairies are of course never a bad thing either :)

Quality-wise it's up to your usual high standards. The obvious question is of course: Is this intended to be a one-shot or were you planning on continuing it? Because as always there are plenty of opportunities for subsequent chapters ;)

Just a few that come to mind immediately:
- Having just experienced vaginal and anal human sex for the first time, Fay is intrigued and keeps coming back each night to experience the many other variations of human sex. Tim has her give him a blowjob that puts the "deep" in "deep throat", fists her (requires some very gradual stretching), has her fist his urethra, etc.
- Alternatively, rather than coming back to Tim each time, Fay explores lesbian sex when she is summoned by a different protagonist; a woman this time. Fay can crawl up the woman's vagina, they can scissor (which effectively turns into fay getting fucked by the woman's clit), some good french kissing can once again force out all of Fay's bones and organs before being sucked into the woman's mouth, etc.
- The curious human (of either gender) can study fairy biology with a bit of dissection.
- Fay tells about her experiences back home and brings along other fairies to learn the ways of human sex as well. Stretch out one fairy and have other climb into or even through her.

As always, looking forward to the next chapter of this story, The Interview, A Cunning Plan, or whatever crazy idea you come up with next.