Green Blood is a manga set in the lawless slums of 19th-century New York, following the brothers Brad and Grave, who survive by taking on dirty jobs for the local mafia. Brad hides a dangerous secret: he dreams of escaping this violent life, while Grave, a cold-blooded killer, fights to protect him at any cost. Readers enjoy the series for its gritty, spaghetti western atmosphere, intense action, and the deep, complicated bond between the brothers as they navigate loyalty, brutality, and the hope for a better future.