Io is a pivotal character in the action role-playing game Code Vein. She serves as the protagonist's constant companion, guiding players through the post-apocalyptic world. Io possesses a mysterious yet gentle demeanor, often exhibiting a deep concern for the protagonist's well-being. As a revenant, she has lost most of her memories but retains a significant connection to the protagonist. Throughout the game, Io's role evolves as she aids in uncovering the secrets of the world and the protagonist's past, ultimately playing a crucial part in the story's resolution.