This one definitely has a taboo feel to it, with the young age of the heroine and the guardian status of the hero. He becomes her guardian after the deaths of both of their very close families in a terrible accident. She's 17; he's 14 years older. Their sexual relationship does not start until she is 18. The story is very focused on these two and their relationship. It's very well written, I think, even if it made me uncomfortable at times.