Sea Dragon Unity (海龍のユニティ, Shīdoragon no Yuniti?), son of Garcia, brother of Seraphina. He is a Blue Warrior from the Bluegrad city in Siberia (the same which appeared in the short story of Hyōga, Nastassja of the Ice Lands Chapter (氷の国のナター シャ編, Kōri no Kuni no Natāsha Hen?) contained in Kurumada's original Saint Seiya manga, tankōbon No. 13) and close friend to Aquarius Dégel. After joining briefly with Dégel and Kardia in order to awake the god Poseidon to plea for assistance to Athena, he is seemingly brutally killed by Rhadamanthys. However, he later reappears in front of Dégel as the Sea Dragon Marina General and schemed to use his sister's body as a vessel to release Poseidon and, with it, take over the world.

As shown in a flashback, he was in despair about the apparent doom of Bluegrad, fated to eternally guard the spirit of Poseidon in the gelid lands and, one day, succumb to the coldness. After discovering the inner sanctum of the god, he viewed himself as chosen by Poseidon as he wore the Scale of Sea Dragon, thus becoming convinced to affirm Bluegrad's hegemony over the whole world. His father Garcia tried to reason with him, but was slaughtered by his own son. While depicted as brutal and power-hungry, Unity actually sought power after the death of his sister, brought by a simple illness they were unable to cure due to their isolation. This drove him into complete despair, so much that he sought the power of the sea god in order to transform Bluegrad in something even greater than Poseidon's own Atlantis.

As the Sea Dragon General, Unity uses Poseidon's power kept in Orichalcum. By using it, he can use the marine organism Coral to regenerate himself and he can freely control it to restrain and manipulate his enemies by invading their nervous system with it, he can also control inanimate objects. His direct attack is known as Holy Pillar (ホーリーピラー, Hōrī Pirā?), in which he creates countless gigantic pillars or whirlpools to crush his enemies.

Unity tried to turn Dégel into his ally, but fought against him when the latter refused. He is ultimately defeated and, apparently returned to his senses, acknowledging the folly of his ambitions. When he renounced his status as a Marina, he lost his power, showing that said power was just borrowed, not his own. He remains an ally to Athena, sworn to protect his friend Dégel's and also Kardia's ideals.