Review of Gangsta.
Gangsta has an inconclusive cliffhanger ending and will probably never receive a sequel. I think those are the two most important facts about this series. After all, the only thing that can occur when adapting a grim and violent manga is censorship for TV and omission of plot details, so why would you bother? Judged by its own merits, this is a fairly odd series. It's heavily focussed on world-building, establishing just what Ergastulum is and how each character fits into its societal fabric. Much of the key plot points and reveals are simply key facts about the world that you might usually expect tobe explained right off the bat, such as who the Twilights are and why they wear dogtags. The other component is a series of melee fights based off a heirarchy of power levels. For instance, the main character, a deaf Twilight, has a dogtag with A/0 written on it, which means he's rather tough (though there's a bit more to that which I won't spoil.)
Although the series has mature themes, the societal problems it tackles are essentially unique to Ergastulum, establishing this as a self-contained fantasy world. This is a series that can only be enjoyed on the strength of its characters and setting - since the story is really rather directionless - but since it spends so much time trying to explain its convoluted premises, there is not much character development in sight. Ultimately it's a confused show that I can't really recommend unless you particularly like its kind of atmosphere.