A cosmic entity of extraterrestrial origin, Green takes the form of an emerald-furred feline to infiltrate human society. Posing initially as the companion of Susan, a Chicago gang leader, it survives her death and bonds with Sango, the orphaned infant son of a slain man. Over decades, Green manipulates Sango by granting his wishes while systematically dismantling his free will, cultivating dependency to further its grand design of global domination.

The entity possesses the capacity to annihilate individuals through enigmatic methods, depicted in visceral detail, and shields Sango from danger during his ascent through criminal hierarchies. It actively severs Sango’s external bonds, including thwarting attempts by Shunsaku, a persistent detective, to intervene.

As Sango matures, Green engineers his rise to power within organized crime, harnessing supernatural abilities to eliminate adversaries and cement loyalty through fear. Its feline guise remains intact unless threatened, whereupon it unleashes a grotesque, otherworldly visage. Countermeasures targeting environmental vulnerabilities—such as depriving it of carbon dioxide—prove pivotal, culminating in Green’s demise when Sango refuses its final command to execute Shunsaku.