Well the anime was more with the start of Kenichi's development and dealings with the 'Ragnarok' group which only went up to chapter 143 or so. Things do start picking up when 'Yomi' and 'One Shadow Nine Fist' is introduced though, not to mention the D of D tournament. It gets a lot more dangerous since Kenichi & co leaves the schoolyard battles into the international arena.
Really hope they are making a second season in the anime. Manga up to chapter 329 for now =)