Sword Art Online: Alicization - War of Underworld is not a character, but an anime story arc and season within the Sword Art Online series. It continues the Alicization storyline, focusing on the escalating conflict in the Underworld and the battle for control of the virtual world. The arc features key roles for Kirito, Asuna, Alice, and other central characters as they face war, sacrifice, and the consequences of artificial intelligence and human intervention.