Soyuz is a young man first known as an Ishigami Village resident, later revealed as the son of the former leader of Treasure Island's Petrification Kingdom. He possesses a muscular physique, a bald head marked by a distinct cross-shaped scar from an infantile storm escape. Typically appearing shirtless in baggy pants, he carries a large shield secured to his back by a rope strap. Born on Treasure Island, Soyuz's infancy was shattered by adviser Ibara's coup using the petrification device Medusa. Ibara petrified Soyuz's father and attempted to kill the infant. A woman, possibly his mother or a loyal servant, aided his escape by boat to Ishigami Village. She succumbed to exhaustion after ensuring his safety, leading to his adoption by an elderly village couple. Despite growing up there, Soyuz experienced recurring dreams of another land and made repeated, storm-thwarted attempts to sail toward it. He concealed his origins, living quietly with fear of exposure as an outsider. Soyuz exhibits a reserved, introverted personality with notable shyness around women, particularly flustered by Amaryllis's charms or Kohaku's presence. Yet he possesses inherent leadership qualities, kindness, and wisdom inherited from his father. Like others in the Stone World, he displays awe toward modern technology introduced by Senku, such as scuba gear, drones, and revival fluid. Crucially, he has an exceptional photographic memory attributed to his mother, enabling recall of infantile events and rapid memorization of complex information like the revival fluid formula. His role expands during the voyage to Treasure Island aboard the Perseus. Initially listed as "Anonymous" due to lacking a formal name, he later reveals "Soyuz" – a name inspired by the space capsule associated with Senku's father, Byakuya. He shares his background with the crew, expressing both desire to discover his origins and fear of rejection. Senku and others reassure him of his place within the Kingdom of Science. Arriving at Treasure Island, Soyuz recognizes it emotionally as his birthplace. He serves as a guide for the scouting party, using his memory to navigate. Discovering Ibara still rules through fear and the Medusa forces Soyuz to confront his past. Seeing his petrified father triggers flashbacks clarifying fragmented coup memories. During the conflict with Ibara, Soyuz is petrified but later revived after Ibara's defeat. Learning his father's statue is too damaged for revival – missing critical fragments making restoration impossible without severe consequences – Soyuz accepts this. He chooses to remain on Treasure Island as its rightful leader, succeeding his father. He commits to reviving the island's petrified inhabitants using his knowledge of the revival fluid and forms an alliance with the Kingdom of Science. As part of this, he requests warrior Kirisame to represent him within Senku's group. His acceptance by the islanders solidifies his role as a unifying figure, blending his heritage with his Kingdom of Science experiences.