This is Yakuza. What are you expecting? There's sex, drugs, violence, betrayal, really bad personalities and such. Though It feels like it sometimes leans too heavily on the ecchi aspect, it never shows anything other than boobs. It merely suggests the act so that the focus of the moment doesnt turn completely into an art scene.
I dont really love this genre since I'm a naive nice guy (I can relate to the MC), but I believe it does resemble Yakuza's theme well. The pride, the greed, the manipulation, the loyalty, the violence, the revenge, the tatoos etc.
Also, it did not feel like a rushed ending at all. Rather, It felt like a movie if compared to other mangas that drag as much as possible until they HAVE to end it. Gekkoh's ending made sense, was unexpected, creative, and built up very well through out the chapters.
----- That said.. some objetive pointers..
Art is inconsistent. some parts are well drawn, some parts are horrible. It does get better as the manga progresses.
Story telling is awkward. Some pages/boxes didnt connect all that well. Sometimes I was like "what? Did I miss something? Did the scanlator mistranslate this?".
As far as manga tecnique goes, it feels like the work of an inexperienced mangaka.
But the story isn't bad, it's totally worth the read.