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.

Badou's in trouble again. He's found some of the "Lost Children," rare genetic experiments left from the past--but so has the mafia. It's up to Heine to bail him out, but the Stray Dog has his own problems now that the enigmatic Giovanni is back on the scene. Meanwhile, Naoto comes to the Underground searching for the killer who wields the same strange black sword as hers. And so their paths begin to converge in the dark and dangerous heart of the city...

Contains an extra story called Dogs: Hardcore Twins in vol. 2.