Aku is a young girl who becomes the first companion of the Demon Lord Hakuto Kunai after he is transported into the world of the game Infinity Game. Orphaned when her parents died of illness, she was ostracized by her village due to her heterochromatic eyes, which have different colors, and was eventually offered as a living sacrifice to a demon king named Greol. She is saved from this fate by Kunai. At their first meeting, she appears disheveled and is limping from an injury to her right leg. Aku has a pure, innocent, and adoring personality. Despite Kunai’s fearsome appearance, she immediately senses the good in him and becomes deeply devoted, addressing him as Demon Lord. She refers to herself using the pronoun boku. Her motivations are centered on loyalty and gratitude, and she serves as a moral anchor that reveals Kunai’s benevolent side. Aku does not possess any special combat abilities or magic, remaining an ordinary human without unique skills or powers. Her value to Kunai is emotional rather than tactical.