Ike Reibun is amazing- so versatile, with consistently awesome art. The characters are drawn so amazingly well. The emotions and the detail put into them is so apparent and amazing. Plus, the character designs really fit- you know when you read some manga with an older guy, and he looks like 16? Well, not so here- Kabu is rugged and masculine, and Nirasawa is pretty dang hot, too, haha. This is pretty hardcore and has a lot of heavy BDSM, smut, and darkness- so if that's not up your alley... read this anyway, haha, maybe it'll convert you. It's very intense, and the yakuza seem a lot more real than anything I've ever read. Of course, I don't actually know anything about yakuza, but this is closer than some, I bet.
The only regret or complaint I have about this manga is that it was definitely too short- I wanted more of the main story! Also, this isn't just smut- you actually really sympathize, and feel with the characters (Kabu and Nirasawa's relationship actually tugs at your heartstrings), and they're not simple; they're realistic in the aspect that you feel like they actually think, and feel. I totally recommend this! It's great- it's smexy, and angsty (although not irritatingly so, and it fits in really well with the whole vibe of the story), not to mention, the art is wonderful, and the story is addicting. It's also got some cute, funny light-hearted moments to break up the dark parts, which are well-placed and greatly appreciated. All in all... just read it!