Sometime in the future, somewhere in Europe, a city has many levels of underground, secret, dangerous levels that have answers to the past. Mihai is a retired assassin who has returned home to settle a vendetta and start a new life as a restaurant owner. Haine was genetically experimented on as a child, which led to him possessing dog-like attributes. Badou is his clumsy chain smoking partner who becomes deranged when denied cigarettes. Naoto was orphaned as a child and has amnesia was trained to wield the sword. Their pasts are somehow connected to the secret underground and the organization that controls it.

(Source: ANN)

Included one-shot:
Volume 2: Dogs: Hardcore Twins

In a post apocalyptic world devoid of seasons, where man's "golden age of technology" ruined earth and caused science to run amok, there live four individuals looking for a door to the hell far below the surface. Through a series of coincidences, the ex-hitman-now-bartender Mihai, the deranged and psychopathic Haine, the vengeful yet kind Naoto, and the freelancer Badou meet one another.

Being a hitman for the government is never easy. And then the girl you like turns out to be...! (Source: MU)