Okay so to start this anime is not for everyone... and by not for everyone I mean thats probably only going to appeal to a select few individuals which include myself. So this anime is pretty much about the Yakuza life. So don't expect any highschool girls with mini skirts and moe bullshit. The OST conists mostly of rap music and its got that "urban" feeling to it that you can also find in some other anime like Michiko to Hatchin and Samurai Champloo.
Story- So the story primarity focuses on the two characters Mera and Kai. its pretty much a revenge tale and also somewhat a tale of redemption for Mera in particular. As the show goes on though, things start to get crazier and crazier. At some point though, you will just start to accept all the craziness and enjoy the story for what it is.
Animation- Now first of all lets talk about the character desings. The people that made this DO NOT like bishounen characters, so don't expect to see any of those(well except for 1). Infact they hate bishounens so much that they ass fuck them to death. No I'm not kidding, I'm pretty sure it happens in the 2nd ep. The characters have somewhat exaggerated lips and sport a wide array of hairstyle from lineups to afros. The backrounds of this anime are particular detailed and the color palette in general is really vibrant and brings out the "urban" atmosphere and brings the city to life. Also a lot of good violence and action scenes for those who look for that.
Sound- Like I said the OST of this anime consists mostly of rap... so if you don't like rap, this is probably not the anime for you. There is some variation, but one of the annoying things is that a lot of the same OST will play throughout the series. This probably wouldn't be so much of a problem, but most of the tracks have lyrics so its really noticable. I really liked the OP and ED themes though and the OST was a refreshing break from all the generic J-pop
Characters- This anime has some really great characters. Although only the two main characters Mera and Kai are fully developed, every characters really plays a role in this anime. I think the best part about the characters is that they don't really fall into any pre-existing archetypes so you almost can't tell what they're going to do/ how they're going to react to a certain sitation. Not to mention the antagonist (Buppa) is one slimy mofo and just makes a really great villain.
Overall- An extremely unique and rewarding experience, if you tired of the current fare of moe and highschool, I can highly reccomend this anime. Also it really helps if you were brought up hard if you know what I mean. Peace.