Ouroboros, Oguri shun is a small time yakuza bossCrows zero Oguri Shun play yakuza bosses son
Gokusen very good as well
Yankii-kun to Megani chan high school romance type but gangster as well
cambrian period is one of my favs
Kid Gang - a comedy K-drama from 2007 that follows three gang members left to care for their leader's baby. It focuses the characters brotherhood and all the crazy things that they get into.
