It's like Yu Yu Hakusho (spirits and the underworld) and 3x3 Eyes manga with a touch of Men in Black and Shinsengumi. I'm at Vol 13. Unfortunately I'm not a big fan of 1 on 1 arena fighting. But at least the fights itself seem faster than Naruto's, and varied and creative like Kenshin's and One Piece's fight scenes. The jokes are funny also.
So bottom-line, IMO, better than Naruto and with an excellent story.

I'm telling ya Helly, you should check out 3x3 Eyes manga. It's much better than the anime.