The problem with Yakuza Girl's plot is it tries to be three different stories in only eleven chapters, and because of this, it doesn't ever really get enough time to build them up to the level where the reader can get involved in them. Foremost the story wants to be a romance between Senguu and Akari, but there isn't much making them a compelling couple, partly because it is made clear that Senguu's reason for transferring is to find a wife and he spontaneously proposes to Akari after meeting her. Akari, for her role, does make a more gradual transition from stranger to lover. That they both improve to the point that they are able to protect each other is nice, as well, but it still feels like a hollow romance.
The second plot thread that the manga tries to spin is Senguu's rise from defenseless loser to ultimate hero. Unlike shonen heroes, he isn't trying to become the best for the sake of being the best, but to protect his new bride-to-be. Still, like usual, this growth in strength comes in the form of (highly lethal) battles with increasingly strong enemies, and there's not much reason to care about Senguu. Have I also mentioned that the villains are usually disgustingly monstrous?
The final aspect of the plot, and the one that would benefit most from more time to develop, is the infighting between the various clans and the apocalyptic conspiracy that makes Senguu so important. At least, I think it was an apocalyptic conspiracy, unless it was trying to stop the apocalypse. And that's the problem: there are about a dozen characters that show up for short periods of time with preexisting conflicts, grudges, motives, and machinations, but by the time one is explained, the story is already dealing with the threat of the next. The finale, especially, is confusing because it is only half explained.
The artwork, like the plot, is very busy. Battles in particular can be confusing to follow because of the constant motion and various effects, abilities, and technique names. Female characters are frequently at least half naked or suffer massive clothing damage and drawn to be alluring and overtly sexual. Males vary from generic to massive and intimidating, while the monster forms of people are detailed almost to stomach-churning levels of revulsion.
Characterization suffers from lack of development, because after cramming in the plot and fights, there's not much time left over for anything else, and so characters are mainly defined by appearance and their specific abilities. This would make remembering who's who difficult, except only four or five characters really matter for the plot.
Ultimately, whether you like this manga or not comes down to whether you're looking for some quick sex and violence (there's no explicit intercourse, but there are two near rapes). If you enjoyed Tenjou Tenge, but thought it spent way too much time in the flashback, this story is worth a look. It won't take long to read, anyway.
One final comment: the ending seems to have some sort of deeper message tucked into that wouldn't feel so awkward if the whole story hadn't been so eager to embrace killing everyone with little provocation.
