It has been roughly one year since Chuuya Nakahara joined the Port Mafia, and the young gravity manipulator has his sights set on earning an executive position. As he works to prove himself, a mysterious figure named Paul Verlaine appears, claiming to be Chuuya's older brother, and vows to assassinate everyone Chuuya cares about. To counter this threat, a European detective named Adam—an advanced artificial intelligence—arrives with the mission of protecting Chuuya from Verlaine, who is known as the king of assassins. Chuuya is forced to form an uneasy alliance with Adam to stop the madman before a fresh storm engulfs Yokohama. Through the escalating conflict, dark truths buried in Chuuya's past come to light, including the answer to his most pressing question: whether he is even human at all. The story unfolds in the wake of the Arahabaki Incident and explores Chuuya's relationships with his former allies, the Flags, and his early life with the street gang the Sheep, while delving into the connection between Chuuya and Verlaine and the origins of Chuuya's extraordinary ability.