I just started reading this, i have volumes 1-5 and im getting 6-8 on saturday (theres about 13), it differs alot from the film, but the basic plot is still there, except kiriyama (the guy who joined for fun in the film) is an actual student who is the son of a mafia boss or somthing. Also, there are alot of weird irrelevent side stories, like mitsuku getting boned by a wrestler.