I can't get away without explanatory notes even on my most banal fic, so it stands to reason this story gets a whole page. Bear with me, please and thank you.
First of all: Yes. I wrote the thing I used to say I never would. I guess I don't really need to justify; there are plenty of authors who do whatever they want, without apology, but after over a decade of maintaining a snowy reputation of Never Going There, I feel like I owe a little explainin'.
My reasons for avoiding mature romantic scenarios in my writing have changed over the years. I shied away from it in the past primarily because I didn't think I could write sensual content in any satisfying way (stop snickering at my word choice, you know what I mean). Most material in this genre is too explicit for my taste, and/or fails to make me care about the characters, much less what they happen to be doing with each other. The relative lack of work appealing to me, to draw inspiration from, meant I was flying blind; everything I attempted made me cringe, and resolve even more not to touch it, ever.
Obviously, that changed. As I've written things over the years that trended more and more in this direction, and then tackled it of necessity in Daughter of the Sea, I discovered that I can, in fact, write compelling romance and even mildly erotic scenes quite well while still respecting my own boundaries of taste and decency. Turns out there are a lot of ways to describe a large gray quadripedic flap-eared long-nosed mammal without using the word "elephant". Go figure.
In developing my own style, I found that vagaries work better than explicitness; at least for me; in romance, as in horror, less is more, because the reader can fill in the gray area in whatever way appeals to (or frightens) them. What bodies do is less interesting to me than what minds and hearts are doing, and those are already vulnerable enough in such moments without putting everything else on display.
My other reasons have been a reticence to write adult material with kids' book origins, and a reluctance to invade the privacy of characters who feel like real people to me. This is more complicated, and I respect the opinions of any who still feel that way, and hopefully they already hit the back button on the browser and just forgot about this. My readers are almost exclusively an adult audience, though, aging further by the day, myself among them. The positive feedback I got on DotS was a factor in my confidence, telling me that people mostly are ok with approaching the stories with an adult's perspectives and experiences. I am also past the point of caring whether everyone approves of my writing choices. At 40+, I feel I've earned that privilege.
From the privacy standpoint, as much as I like to pretend Taran and Eilonwy are real people...they aren't. But meanwhile their fictional relationship is so complex, emotional, hilarious, compelling, and heartbreaking; it was, perhaps, inevitable that I eventually explored aspects that could be revealed only in the context of intimacy, an intensity matched by little else in the human experience. There is so much to unpack in their connection and the way it is all wrapped-up in the series' conclusion, but it's given incredibly short shrift, even taken in context. The complexity and tension that would always exist between them thanks to Taran's choice is a real land mine of subconscious feelings, and I wanted to blow a few up to see what happened.
I also wrote this in part as an answer to what I think is a misguided but irritatingly popular attitude that Eilonwy was given short shrift by choosing marriage over keeping her (totally useless, incidentally) magic and eternal life in the Summer Country. I understand the feminist qualms here, but it completely misses the fact that this choice is one of the only ones in the entire series that fully exercises her agency. Marrying doesn't sell her out; she doesn't "need a man" but she does need Taran, just as he needs her; and this type of unity is a strength, not a weakness. It's complex, and bittersweet, and there is still plenty to criticize about the way she is sidelined in the later books, but this is not the hill to die on, IMO.
So there you have it, and you don't have to review if you're embarrassed; I get it. Hope you enjoy anyway. Maybe not as much as the protagonists do, but I won't judge. ;)