Eugeo Herlentz is one of the secondary protagonists of the Alicization arc of Sword Art Online. He is an extremely skilled swordsman, as well as Kirito's best friend, and partner, and the childhood friend and love interest of Alice Zuberg. After being killed by Quinella during the battle of the central cathedral, he is later on resurrected under the identity Eolyne Herlentz, but had lost his memories of Kirito, Alice, and his past self. However, he later on regains his memory, and reassumes his original identity.
Eugeo is voiced by Nobunaga Shimazaki in Japanese, and Brandon Winckler in English.