archange du mer's Things

As written on the tin; i'm very certain it was shounen but it might have been a yaoi

What i remember is that there's this guy who gets abandoned in some sort of a dark forest, presumably as a sort of sacrifice to the demon/vampire lord that lives there, and instead of eating him or something the vampire takes in the kid and teaches him martial arts over several years? And the now young man wants to sta with the vampire but the vampire doesn't want to eat him for whatever reason

Like i said, the art was gorgeous, almost iridescent in some way. Full color, some of the early panels feature a snowy forest and someone, i think the main character, on horse back.