In the story, Seiya is one of the 88 mythical warriors that have served the goddess Athena during ages, protecting justice and peace on Earth, and are known as "Saints, the bringers of hope." As a Saint, Seiya dons one of the radiant and powerful armors of divine origins known as Cloths, his representing the constellation of Pegasus. He also possesses superhuman strength and speed, two of the many extraordinary abilities the Saints draw from their guardian constellations and an inner essence called Cosmo.
Seiya is the main character of his namesake series, Saint Seiya. He is one of the eighty-eight saints of Athena, and serves loyally at her side. Seiya draws his Cosmo from the constellation that connects to the Cloth. At the start of the series, Seiya's main objective is to find his older sister Seika, who disappeared from Japan when Seiya was sent to train to become a Saint. However, as the series continues, Seiya eventually starts fighting alongside the other Bronze Saints to protect Athena, albeit reluctantly at first. During his childhood in Greece, he met Eagle Marin, a female Silver Saint who trained him to become a Saint. Due to her similarities to Seika, Seiya starts thinking Marin is his sister, but later he discovers he was wrong and find his real sister. Seiya tends to be the most immature Saint, as he frequently makes jokes and is not quite concerned about the consequences of his actions.
Although Seiya began his journey as a Bronze Saint, the lowest of three ranks, his abilities gradually grow to rival those of the Gold Saints, the most powerful of Athena's soldiers. He achieves this by awakening his 7th sense, the essence and origin of the Cosmo. Before descending into the realm of Hades, he also awakes his 8th sense Cosmo, allowing him to enter into the Underworld without being subject to its laws. His most-seen technique is the Pegasus Meteor Fist which initially allows him to send a large number of punches in a second. Seiya starts this attack at Mach 1 speed, and later develops it to achieve lightspeed for a few seconds. Seiya can combine all his meteors in one punch called the Pegasus Comet Fist . His most powerful technique is Pegasus Rolling Crush , where he grabs hold of his opponent from the back, soars miles into the air, then suicide-dives head-first into the ground.The Pegasus Cloth represents the Pegasus constellation, which is associated with Pegasus, the divine winged horse from Greek mythology. Seiya defeated 10 other trainees in order acquire the Pegasus Cloth and the status of Saint of Athena. The Pegasus Bronze Cloth suffers damage various times throughout the series, with Aries Mu typically responsible for repairs. In Kurumada's manga, the Cloth changes shape each time it is fixed, with each revision evolving the Cloth into a more detailed form while it remains the same in the anime until the series' second arc. When the Gold Saints use their blood to revive the Bronze Cloths, the second version of the Pegasus cloth can change from bronze to golden hue whenever Seiya charges his Cosmo to the maximum. With the Cloth that Seiya uses in the Hades arc, Seiya is able to use the wings to fly, both normally and through dimensions. In his fight against Thanatos, resurrects in God Cloth state, which was last seen in the ages of myth, further increasing Seiya's Cosmo and vitality.
Eventually, Seiya becomes powerful enough to wear the Gold Cloth of Sagittarius, a Cloth that had lost its true owner before the series began. When Seiya has the Gold Cloth on, his Cosmo is magnified. Nevertheless, while Seiya uses the Sagittarius Gold Cloth many times throughout the series to save Athena from certain peril, he is never officially granted ownership of the Cloth.