Seiya, a Japanese orphan recruited by the Graad Foundation, trains in Greece to become the Pegasus Bronze Saint under Eagle Marin. His drive centers on reuniting with his sister Seika, separated during his training. Unknown to him initially, he shares billionaire Mitsumasa Kido as a father with fellow Saints Dragon Shiryu, Cygnus Hyoga, Andromeda Shun, and Phoenix Ikki, making them half-siblings. Seiya displays unwavering determination, refusing surrender against impossible odds. His impulsiveness and outspokenness often seem insolent, yet conceal a core of kindness, fairness, and fierce loyalty. He prioritizes protecting allies, shows mercy to defeated foes, and employs tactical cunning in combat. He typically avoids fighting female opponents like Silver Saint Shaina, though context occasionally overrides this principle. His power derives from manipulating **Cosmos**, an inner universe granting superhuman strength, speed, durability, and energy projection. Signature techniques include the **Pegasus Meteor Fist** (high-speed punches) and **Pegasus Comet Fist** (concentrated energy strike). Through trials, he awakens advanced senses: the **Seventh Sense** (Miraculosity) against Taurus Aldebaran, enabling light-speed movement and god-level power; the **Eighth Sense** (Afterlife) during the Hades conflict, allowing soul and body control in the Underworld; and the **Ninth Sense** (Godhood), tied to divinity. His endurance lets him survive assaults from Gold Saints and gods, often recovering swiftly. His Pegasus Cloth evolves in battle, growing wings for flight during the assault on Hades' realm and later manifesting as a **God Cloth** in Elysium. In the Hades Chapter—Sanctuary segment, Seiya ignores Athena's order to avoid the Sanctuary, intervening against Hades' invasion. He witnesses resurrected Gold Saints—Gemini Saga, Aquarius Camus, and Capricorn Shura—attacking allies like Aries Mu. Persisting despite grave wounds, he confronts Specter Wyvern Radamanthys. Using the Eighth Sense, he enters the Underworld, joining Athena's mission against Hades. During Elysium's final battle, he and allies gain God Cloths empowered by Athena's blood. Seiya sacrifices himself to shield Athena from Hades' sword, suffering a near-fatal curse. His armor shifts from a damaged Pegasus Cloth to a third variant in Underworld conflicts.