 If you liked
Rokudenashi Blues
|
 ...then you might like
Osu!! Karate-bu
|
They both have a similar setting and story. They're about Japanese delinquent teenagers becoming gangsters so they can fight each other. It's not an in-depth recommendation, I know, but they're both definitely worth reading for their own set of quirks and characters, and fans of one will definitely enjoy the other.