As she continues her Chroma work, Marona's path eventually crosses with that of a man named Walnut. Walnut prides himself on his status as a Chroma Oxide, one who secretly follows a Chroma on their mission and steals the reward for their work. Walnut regularly tries to meddle in Chroma-related matters involving Marona, but is rarely successful. As they continue their work, Ash and Marona also meet a sickly young girl named Castille. Confined to her bed or wheelchair for most of her life, Castille has been unable to go out into the world and make friends. However; after helping Castille's family on an assignment, Marona grows close to Castille and they become friends. Marona leaves Putty—a mischievous nature spirit found on an earlier assignment—with Castille to keep her company when Marona is unable to do so.