Eugeo is the deuteragonist of the first half of the Alicization Arc. Eugeo was a child born in a remote village in the Human Empire of Underworld where he was assigned the Sacred Task of felling a giant tree with his childhood friend Kirito. After a mishap during an adventure to the mountains resulted in his other childhood friend Alice Zuberg being apprehended by an Integrity Knight for breaking the Taboo Index while his memories of Kirito were sealed by the administrators of the world Eugeo spent the following six years focusing on his work to avoid thinking about his lost friend until Kiritos return to Underworld led to Eugeo building the resolve to embark on a journey to become an Integrity Knight himself to rescue Alice as well as acquiring the skills to wield the Blue Rose Sword he had retrieved from the mountains where Alice had broken the Taboo Index. Source: SAO Wiki