From Viz:
MIHAI, the "Weepy Old Killer": A former hitman now trying to live a quiet life but haunted by the deaths of his victims and his lover. BADOU, the "Gun Smoker": A chain-smoking "information broker" and hired gun whose reckless façade hides a serious intent. NAOTO, the "Blade Maiden": A preternaturally skilled swordswoman with a single desire: revenge against the assassin who cut down her family. HEINE, the "Stray Dog": A cipher with a metal collar bolted to his neck, a disturbing talent for mayhem, and a childhood sacrificed to the thing known as "Kerberos."
Driven by their ghosts, both dead and alive, and their desire for truth, all are struggling to solve the secrets of the past while surviving the dangerous present by gun and sword and courage and luck.