Set 7 years before the events at the beginning of the original Saint Seiya Manga, and 6 years after the death of the Gold Saint Sagittarius Aiolos, Episode G revolves around Athena's Saints, humans with superhuman powers who are devoted to the Goddess of War Athena, and whose duty is to protect the world from evil. The protagonist is the Leo Gold Saint, Aiolia, who is mistrusted by the rest of the Saints because of the seemingly traitorous actions of his brother Sagittarius Aiolos in the past. In turn, he holds a grudge against the Saints as a whole, and against the elite order of the Gold Saints in particular. While the Pope, the leader of the Saints, sends Aiolia on mission after mission to prove his loyalty, evil forces manifest that threaten to destroy Sanctuary, the home of the Saints. A modern-day Titanomachy begins as the Titans, ancient gods with a desire for revenge on the Olympian gods, attack Sanctuary to retrieve the "Megas Drepanon", the weapon into which Zeus had sealed their King, Kronos, in the age of mythology. Their first assault is thwarted by Aiolia, who subsequently gains the attention of the Titans as the "man of the evil omen" who is destined to free their King. With the Titans once again roaming the Earth, ancient monsters are also resurrected worldwide and the Saints have to deal with them.
