Orphaned and separated from his sister Seika after recruitment by Mitsumasa Kido, Seiya de Pégaso trained in Greece under Eagle Marin to become a Saint serving Athena. His primary motivation evolved from locating his missing sister to protecting Athena and Earth from divine threats. He obtained the Pegasus Bronze Cloth by defeating Cassios in sanctioned combat, though initially resisted employing its power beyond personal objectives. His personality combines unwavering determination, resilience against impossible odds, and fierce loyalty to allies and Athena. He demonstrates strategic battle analysis of opponents' weaknesses and compassion toward enemies, yet exhibits impulsiveness and defiance toward authority figures like Athena when their commands hinder his protective instincts. During the Hades Chapter - Sanctuary arc, Seiya disobeyed Athena's explicit sanctuary ban upon sensing danger. He intervened when Aries Mu faced overwhelming odds against resurrected Gold Saints Cancer Deathmask and Pisces Aphrodite, now serving Hades. Despite Mu's initial rejection of assistance due to loyalty to his resurrected master, Seiya persisted, displaying combat prowess sufficient to challenge the revived Gold Saints. His involvement ceased when specter Wyvern Rhadamanthys struck him from behind during distraction. This arc revealed Seiya's evolved capabilities: achieving light-speed movement and accessing the Seventh Sense to temporarily rival Gold Saints' power. His Pegasus Meteor Fist attained hypersonic velocities. Following Athena's ritual suicide to reach the Underworld, former Pope Aries Shion repaired and upgraded his armor to the "Final Bronze Cloth" using Athena's blood, enhancing durability and power for impending battles against Hades' forces. Seiya's broader journey saw him advance from Bronze Saint to recognized successor of the Sagittarius Gold Cloth, originally worn by Aiolos. He participated in pivotal conflicts against Poseidon and Hades, contributing to both gods' defeats. In the final Elysion battle against Hades, he suffered a curse from Hades' sword that induced coma, directly prompting Athena's time-travel quest in "Next Dimension" to save him.