Is Quartet coming back?

Shun, who has tattoos and piercings all over her body, is the third generation descendant of a Japanese orphan left behind in China during World War II. Takeru is a lonely and reckless hooligan whose family was murdered when he was a child. Shun, Takeru and Kasumi with an equally troubled past and background, become collaborators after being hired by Kuchinawa in police undercover operations in the city of 'Midori', a neighbourhood for illegal residents. They infiltrate a criminal gang to investigate, and find illicit human drug experiments and slave treatment staring them in the face. They grow to trust one another and mature through this experience.