In a dystopian society of drugs, gangsters, and evil souls, only one thing reigns true: death is the only way out for ninjas. Infected with a mystical ninja soul coated in fury, Ninja Slayer is born. Barely escaping death and losing his family to a pack of ninjas, Ninja Slayer sets out to avenge the death of his loved ones by spraying the blood of ninjas all across the hell-world of Neo-Saitama.