I didn't want to make a review, but here's an idiotic comment up here that really hit my nerves, so now I will. The whole manga looks a lot like classic western comics and the characters' behaviours feel mostly inspired from mafia movies, with some coming straight out of western in the latter half (Indians and Ned felt straight out of Tex). Some elements of the art do draw from other manga culture, but this really is, by all means, a western comic written by Japanese author.
What really got me furious was this: "Second, the revolver gunblade. Please don't bring Final Fantasy weapons into a 'historical' setting". This moron has no knowledge of historical weapons and thinks he can cast aside things as fantasy just because he knows nothing. Gunblades are a thing, they developed in various ways from the late XVI century to this day and they had a moment of great variety and experimentation in XIX century USA, though the largest use was probably seen when Polish cavalry adopted gun axes as ordinance weapons between the XVI and XVIII centuries, for 200 years. But no, for this guy it's just final fantasy. The specific gunblade design used by the main character Brad, to be exact, is the .54 caliber Elgin pistol, equipped with an 11.5 inch bowie knife blade, adopted by the US navy in 1938 and used in some instances during the US Civil War, so it is the absolutely perfect weapon for this setting.
Third: gang tattoos. If anyone thinks gang don't use specific gang tattoos in a variety of areas of the world, means they never bothered learning the first thing about neither tattoos or gang culture.
To add something more to the historical validity of this comic, most major events clearly draw inspiration by real world history, changing the characters and maybe raising the death toll a little. Clearest example is the direct reference to 1857 Dead Rabbits riot, which I suggest you don't read about if you don't want to spoil the story.
Other than that, the manga is very good, compact, fast paced, with a good play on tension, keeping the reader on edge for the possible twists and turns of the story, that often caught me by surprise. The art is extremely detailed and probably the strongest point of the manga. It's technically perfect, but lacks that special something for me to give it a 9.
P.S. My criticism also applies to @residentgrigo who also came bitching about historical accuracy without even doing a basic research on the topic. Literally just look up the Five Points on Wikipedia ffs
