The main character is a young teenager who is a known trouble maker, though he is actually a pretty nice guy.
He ends up getting himself killed and becoming a servant for the prince of the afterlife, he develops spirit techniques which he soon advances and is sent on missions to capture demons and eventually enters a whole new world full of demons, and enter into a huge arena style tournament, this is one of the greatest arena fighting anime i have seen.
Their's Adventure and mystery in this anime, as well as him eventually discovering facts out about himself, there's plenty of battles here.