Although it isn't tagged as comedy, I think any one who reads it will agree that it is.
For staters, the art is probably some of the best I've seen and quite different from this author's other work, 1/2 Prince. If your looking for a manga similar to that, I wouldn't recommend reading this.
Most of the characters have outer facades they work hard on maintaining. Why? Because as a guardian/knight, they each have "images" to keep. The main protagonist is Creus Sun, the Sun knight. Usually, it's quite hard to place good sarcasm in manga but here, it's very, very amusing.
As for the plot, because of
it's supernatural elements and conspiracies *ahem*, there are a few points that can be misleading which, of course, keeps it interesting especially with the humorous overtones.
If your looking for a sarcastic and witty manga, look no further and give this manga I try. It's a bit slow on updating but also one of the few manga I don't mind reading over and over again =D
WARNING: If your overly-religous, then do NOT read this manga. It doesn't necessarily mock religion but you might find it offensive it some ways. If you still insist on reading it, I won't (or rather can't) stop you but hey, I warned you.