The Holly King and the Oak King
The Holly King and the Oak King is a story written by Kagamino Kage and illustrated by Nanashi. It ran in Issue 8 at http://s2b2.livejournal.com/36268.html, and is mirrored at http://www.shousetsubangbang.com/mirror/the-holly-king-and-the-oak-king/.
From the author: "Homoerotic rewrite of somewhat controversial myth. Shamelessly melodramatic; non-conish."
Whether it is the Holly King or the Oak King who is slain at Yule seems to be a matter of some debate, since I've seen it stated both ways from different sources. Hell, I even had one person tell me that Graves and/or Frazer completely made up the myth, but I doubt that's true. (And given that this is not only fiction but porn, I don't really care, either. xP) But the general consensus seems to be that each King is slain at the height of his power, signifying that the end of the season is coming - thus the Holly King is slain at midwinter, heralding the return of spring. So, I went with that interpretation. (And considering that Mr. Holly was on top, I thought that made for a delightful little yin-yang dynamic, ahaha. :D)