Been meaning to dig into this for awhile now. In the middle of the [SPOILER - highlight to read]: prison story.
With all the comparisons to Ippo, I was thinking of something along those lines, but it's nothing like Ippo at all. It has this weird mix of cutey cartoony with grimy realism.. Cute as a button homeless kids, a protagonist living on the street who catch's the notice of a down and out former boxer who is literally laying in the gutter with a bottle, metaphors for rape.. I'm sure this is a style that must have been popular at some point, but it's all fairly shocking to me.