Eugeo is a central character in the 'Alicization' arc of Sword Art Online. He is a childhood friend of the protagonist, Kirito, and hails from the Underworld, a virtual realm within the series. Eugeo is depicted as kind-hearted and determined, often showing a strong sense of justice and loyalty. Throughout the series, his primary goal is to rescue his childhood friend Alice, who was taken away due to the Integrity Knights' laws. Eugeo's journey alongside Kirito is integral to the story, as it explores themes of friendship, sacrifice, and the quest for freedom.