Gang King

The lead character, Jimmy (Katsuya Oonishi) is an art student at Bara-Gaku ('Bara Juuji Gakuin'; Rose-Cross Academy). When he was little, he almost drowned, but was saved by a tattoo artist. From that day, Jimmy vowed to become a tattoo artist (because tattoos signify 'a hero' to him).

Jimmy's a decent person by nature, but because of the people he hangs out with, he's considered a delinquent. Banko, his partner-in-crime, is a shrewed kid; he sells information on the popular girls (phone numbers, likes and dislikes, etc) in the area. Despite the delinquent exterior, Banko is actually really smart and has broad general knowledge.

As the story progresses, Jimmy and Banko meet new people and they form a gang of their own; along the way they bump heads with other gangs from other schools/districts. This manga is not the typical high school-slice-of-life story; it's got a rougher edge! This manga depicts some high school delinquents trying to get through high school life and gang fights.

(Source: Mangahelpers)

Included one-shot:
Volume 17: Smile (with Nagata Kouichi)