"Knights of the Zodiac: Saint Seiya" centers on a group of young warriors known as Saints, who are tasked with protecting the reincarnated goddess Athena and maintaining peace on Earth. Each Saint wears a powerful armor called a Cloth, modeled after constellations, and draws strength from their Cosmo, an inner energy tied to the universe. The story primarily follows Seiya, a determined and courageous teenager who becomes the Pegasus Saint after enduring rigorous training to earn his Cloth. Alongside him are other Bronze Saints: Shiryu of the Dragon, Hyoga of the Cygnus, Shun of the Andromeda, and Ikki of the Phoenix. Each character has a distinct personality and backstory, contributing to the group's dynamic.

The narrative begins with Seiya participating in the Galactic Tournament, a competition to determine the strongest Saints. However, the tournament is interrupted by the revelation that Athena has been reincarnated as Saori Kido, the granddaughter of Mitsumasa Kido, the founder of the tournament. Saori's true identity is revealed, and the Bronze Saints must protect her from various threats, including the Gold Saints, elite warriors who serve as guardians of the twelve zodiac temples. The Gold Saints initially oppose the Bronze Saints, believing them unworthy of protecting Athena, but conflicts arise due to internal corruption and betrayal within their ranks.

As the story progresses, the Bronze Saints face increasingly formidable enemies, including the Silver Saints and the powerful Gold Saints. Each battle tests their resolve, strength, and loyalty to Athena. The Saints must also confront their own personal struggles and past traumas, which are often explored through flashbacks and character development. The narrative delves into themes of friendship, sacrifice, and the pursuit of justice, as the Saints fight to prevent the resurrection of malevolent forces that threaten humanity.

The series is structured around several major arcs, including the Sanctuary Arc, where the Bronze Saints must overcome the twelve Gold Saints to reach Athena and save her from a deadly fate. Later arcs introduce new adversaries, such as the Poseidon Arc, where the Saints face the sea god Poseidon and his marine generals, and the Hades Arc, which pits them against the underworld's ruler, Hades, and his Specters. Each arc builds on the previous one, expanding the mythology and stakes of the series.

The characters' growth is a central focus, with Seiya evolving from a brash and impulsive fighter into a selfless leader. Shiryu embodies discipline and honor, Hyoga grapples with his emotions and past, Shun represents compassion and inner strength, and Ikki, initially a lone wolf, learns to trust and fight alongside his comrades. Their interactions and shared battles highlight the importance of unity and perseverance in the face of overwhelming odds.

"Knights of the Zodiac: Saint Seiya" combines action-packed battles with a rich mythological backdrop, blending elements of Greek mythology, astrology, and martial arts. The series is known for its dramatic confrontations, emotional depth, and intricate lore, making it a cornerstone of the shonen genre.