Gemini Kanon debuted as the ambitious younger twin of Gemini Saga, sharing the constellation. He openly embraced power-seeking desires and tried to persuade Saga to assassinate Pope Shion and the infant Athena to rule Sanctuary. After Saga refused and imprisoned him at Cape Sounion, Kanon discovered Poseidon's trident during confinement, releasing the god's spirit. Posing as the Sea Dragon Marine General, he manipulated Poseidon's forces by orchestrating the god's premature awakening through the human host Julian Solo. Kanon aimed to use Poseidon to destroy Athena and later overthrow the sea god, but the Bronze Saints thwarted his plans. Following Poseidon's defeat, Kanon survived and expressed remorse. He sought redemption by aligning with Athena, though Sanctuary's Gold Saints distrusted him due to his past. During Hades' assault on Sanctuary, Kanon guarded the Gemini Temple. He intercepted the resurrected Gold Saints—including his brother Saga, Capricorn Shura, and Aquarius Camus—sent by Hades to kill Athena. Using the Gemini Cloth and mastery of illusions, particularly the "Labyrinth of Twins," he delayed their advance. When confronted by Scorpio Milo, Kanon submitted to the Scarlet Needles without resistance to prove his loyalty. Milo's final needle stopped his bleeding, signifying acceptance of his redemption. Athena then tasked Kanon with delivering the golden dagger to the resurrected Saga, symbolizing trust and closure. In the Underworld, Kanon fought alongside Athena's forces against Hades' army. He employed psychological tactics, controlling the specter Balrog Lune to locate the Wyvern judge Rhadamanthys. After a fierce battle, Kanon overpowered Rhadamanthys with the Genrou Maou Ken technique. As the Gold Cloths resonated to destroy the Wailing Wall, Kanon removed his Gemini Cloth, sending it to aid the effort. He sacrificed himself by trapping Rhadamanthys and unleashing a final Galaxian Explosion, destroying both himself and the judge. This act completed his atonement, allowing the Saints to advance toward Hades. In spin-offs, Kanon appeared as the Pope in *Saint Seiya Episode G Assassin*, aiding allies under threat. *Saint Seiya: Saintia Sho* depicted his evil persona revived as the War God Ares, though his connection to Eris remained ambiguous.