tl;dr: A really solid manga with great pacing and an art style that works really well, but that has an unfathomably terrible ending. 

This manga's best aspect is that it is incredibly well paced. In general it feels like the flow to the manga has three parts intermixed. The first is just comedic small stories, featuring the various characters doing random things, generally involving mafia related subjects with some character development maybe, but not much in terms of overarching plot lines. The second is the buildup portion. Here, some sort of conflict is developed in terms of providing background behind why it's occurring and establishing a motivational basis behind why Ken and the gang are fighting. This buildup leads to a long climax portion where major fights go down, back to back, and Ken comes out victorious and advances along with his gang to a new stage. These three aspects are for the most part paced incredibly well, where the story just continues to flow well, never feeling like it's getting dull or dragging on, and thus keeping the reader enthralled throughout. There are three main reasons for that, the first being that there are a lot of amusing characters with many being quite likable. Ken gets some solid character growth throughout and comes out looking very much a boss constantly. The other characters don't really grow much, but they're have pretty well defined and distinct characters that work well. The bonds developed between them though are developed especially well, both for the gang and between Ken and Yumi. There is somewhat of an issue though, in that most side characters outside the gang and Yumi just sort of disappear after the arc they're focused on, which felt like somewhat of a waste. The second reason the pacing is so great is that the comedy is really solid and pretty varied throughout, which keeps it entertaining on a smaller scale. And the last reason is that the art works incredibly well and is often enjoyable in its own right. The art is very different from most manga, but it works really well. It's rough, but it has a lot of personality to it such that it works well with the gritty atmosphere, both in terms of the violence and ero, both of which are quite gratuitous and add quite a bit to the series. Unfortunately, there is problems with the final arc and how it ends. When the final arc, going up against the White Dragon Clan begins, it gets really messy and drags on too long in terms of buildup with things going on behind the scenes and focusing on new unimportant characters that ultimately don't have much of an impact and aren't made especially likable. That isn't much of an issue however, as when that arc reaches its climax, it's incredible. The culmination of the relationship with Yumin, everyone fighting against the various members of the clan, things escalating tremendously, things finally coming to a close, it's all incredible. The problem, is that even though at this point it feels like it's been set up to end in a pretty satisfying manner that provides adequate closure, it then randomly has one final random twist that then ends up pushing it towards what may well be one of the worst endings I have ever seen in a manga, one that's pointlessly long, doesn't make any sense in terms of plot threads, character personalities and relationships, and isn't entertaining at all, an absolutely horrible fumble of what could have been a really solid ending. It's an ending that leaves me with an incredibly bad taste in my mouth regarding the entire thing. Still, the journey from beginning through to right before the ending was quite incredible so I'd say it's still worth a read. The side stories were amusing too.