With a mix of humor, eroticism, and twisted romance, SHOUJYO introduces the world of Tomokawa, a notoriously lazy policeman who spends most of his time having affairs with married women or hanging out with his friend Sukemasa, who has an intellectual disability. One day while out at a bar, he is approached by 17-year-old Yoko, who quickly falls for him. Yoko, it turns out, is Sukemasa's sister, and both girls are the children of his old flame Yukie, a cruel woman. Tomokawa soon takes both teens under his wing, attempting to protect them from their heartless mother. But can these relationships last in the face of social disapproval?