and the closing theme is “Half Pain”, both songs by “Bana”:
Very moody and evocative, much like the anime.
Here is an excellent review of the anime, or you can always hit Wikipedia.
Anime music: “Witch Hunter Robin” opening and closing themes
So, in honor of “Throwback Thursday”, I present the opening and closing themes to one of my favorite anime from a few years back (12!), “Witch Hunter Robin”. The opening theme is called “Shell”: