Eugeo is a central character in the 'Alicization' arc of Sword Art Online. He is a skilled swordsman and a childhood friend of Kirito, the protagonist. Raised in the Underworld, a virtual world, Eugeo is driven by a sense of duty and loyalty. His primary goal is to rescue their friend Alice, who was taken away by the Integrity Knights. Eugeo's character development is significant as he grapples with his emotions, the nature of reality, and his ultimate purpose in the world he inhabits. His journey is pivotal to the storyline and Kirito's growth.