Soyuz (ソユーズ Soyūzu) is a former member of Ishigami Village and the long-lost son of the leader of the Petrification Kingdom. After Ibara's defeat, Soyuz claimed his rightful place as the leader of the Petrification Kingdom, enlisting Kirisame as his replacement within the Kingdom of Science’s ranks.
Soyuz is a young man, with a bald head, large round eyes and a distinct cross-shaped scar on top of his head.
He is shirtless, wears a large shield on his back held by a rope strap that is slung around his shoulder, and baggy pants that reach only past his knees.
Soyuz is a quiet and reserved man living in Ishigami VIllage. He is rather shy when it comes to women, incapable of resisting the charms of Amaryllis, and becoming incredibly flustered around Kohaku when she changes.
Being royalty himself, he has his father's kindness and wisdom, a natural leader just like him.
Abilities and Skills
Soyuz possesses an incredible memory, able to remember things from even when he was a baby. When searching for the petrified people who fell into the sea, he was able to remember where the people were thrown from and the way they were moved by the currents, implying he has a photographic memory. He also managed to memorize the formula of the Revival Fluid in a short amount of time. It is later revealed that this is because he inherited his mother's great memory.
Little known about Soyuz’s childhood life, he was a child of the leader of the Petrification Kingdom.
During Ibara’s hostile takeover on his home kingdom, he made an attempt to kill the infant Soyuz, however, the said infant was saved by a young woman who was loyal to his father and ended up being framed by Ibara as a kidnapper attempting to kidnap Soyuz. Thanks to the woman's sacrifice, Soyuz ended up in Ishigami Village safely.
He is selected to be apart of the crew of the Perseus, Ryusui notes that he doesn't have a name.
During the voyage to Treasure Island, he reveals to the others that he was actually from outside Ishigami Village, having drifted there when he was a baby. He then leads the others to the island where he came from.
When they learn of Amaryllis' plan to infiltrate the harem, they realize she needs help to do so. Soyuz was shocked to realized that Kohaku was needed to do so. He was worried about the plan because of her tomboyish nature and lack of etiquette.
Soon they witnessed Ibara and his men storming the Perseus. When Kohaku yelled the word lab, Soyuz realized that only someone from the Kingdom of Science would know that word and believe she was trying to find a survivor.Surely enough one of the survivors turned out to be Ginro. Soyuz was disappointed that it was him along with the others, especially when he begs them for help. However, Ginro with help from Suika were able to reclaim the mobile lab and sneak by the enemies who mistake it for an animal.
He aids in the construction of the oxygen tanks and they are complete after several hours. When they are done, he is amazed actually breathe underwater. He and Ryusui look for the petrified who were thrown into the ocean. With his exceptional memory and help from a depetrified Taiju, they manage to find all the people who were tossed into the ocean, though Soyuz was amazed by Taiju doing it it single-handedly before offering him a ride in the boat. 
He helps Yuzuriha Ogawa repair the broken statues, using his memory to distinguish them. When a frantic Amaryllis reports on her experience, Soyuz is shocked to hear he might be related to the original leader. 
The group then decide to split into groups with one deciding to show the whole petrification kingdom the true state of the head. However they discovered that his statue was already destroyed by the evil minister but Yuzuriha planned to recreate the statue. While doing so, he finally recalls his memory of him while become happy at finally reuniting with his father.
They eventually succeed and Soyuz is disappointed to hear that his father can't be revived because he is missing pieces. 
He notices Oarashi running in a frenzy and realizes he plans to head to the island's center and Ukyo has Taiju yell to the others on this. After Taiju tackles him, they are warned by Amaryllis to throw away the device since Ibara likely activated it but Oarashi had swallowed it and it activates, to Soyuz' horror.
When Ibara petrified the island, Soyuz and his allies put their faith in Senku to win. Ibara came across the statue of Soyuz and taunted him on coming home to fail.
Once Ibara is defeated, Soyuz is revived by Senku. Soyuz helps Senku and the others revive their allies. He is dismayed when Kirisame kneels to him, during the celebration.
He recognizes the shape of the device once the group are confused by Whyman's call. Soyuz helps Taiju with bringing up the unidentified statue. The symbol on the person's detached arm is the same as the shape of the petrification device. Soyuz reattaches the arm and watches the man being revived.
Soyuz joins the others in reviving the islanders, although he is disappointed to hear that his father can't be revived. Regardless, he is recognized by the islanders as the leader's son. The next day, he decides to stay behind and become the new head of the Petrification kingdom. He tells Senku that he remembers how to make the revival formula and will be reviving the remaining petrified islanders. He asks Kirisame to take his place within the Kingdom of Science to defeat the Whyman. A teary eyed Soyuz bids his friends farewell, as they sail off.
- "Soyuz" means "union" in Russian.
- His name is the same as the spaceship that led Byakuya, Lillian and Shamil to the ISS in Chapter 43, the Soyuz.
- He uses a sickle and a hammer which is the symbol of the USSR.
- The X on his head is a reference to the presence of the astronauts' treasure on his native island.
- Although first appearing in Chapter 17 he was nameless until Chapter 101.
|Male||Alabaster • Argo • Carbo • Chrome • Ganen • Genbu • Ginro • Hagane • Jasper • Kaseki • Kinro • Kokuyo • Magma • Mantle • Natri • Sagan • Sho • Soyuz • Tetsuken • Titan • Unmo|
|Female||Alumi • Azura • Beryl • Dia • En • Garnet • Kohaku • Kujaku • Namari • Ruby • Ruri • Sango • Sapphire • Shirogane • Shovel • Suika • Suzu • Turquoise|
|Unknown||Chalk • Sagara|
|Male||Chrome • Gen Asagiri • Ginro • Hyoga • Kaseki • Kinro • Kokuyo • Magma • Matsukaze • Mozu • Ryusui Nanami • Senku Ishigami • Taiju Oki • Tsukasa Shishio • Yo Uei|
|Female||Homura Momiji • Kirisame • Kohaku • Minami Hokutozai • Nikki Hanada • Ruri • Suika • Yuzuriha Ogawa|
|Male||Chrome • Ginro • Jasper • Kaseki • Kokuyo • Kinro • Magma • Mantle • Soyuz • Tetsuken • Ibara • Mozu • Oarashi • Matsukaze|
|Female||Garnet • Kohaku • Ruby • Ruri • Sapphire • Suika • Shirogane • Shovel • Turquoise • Amaryllis • Kirisame|