Ceroba's reaction to Clover arriving in the Wild East is polite and cordial. However, if Clover has killed any monster before meeting her, Ceroba will notice as if by a sixth sense, and refuse to travel with Clover beyond the town. If Clover has been merciful, and killed no one, Ceroba will reveal to him that she's worried about her daughter, who was sent to the True Lab after falling ill - she hasn't heard anything in a long time. She insists on escorting Clover through the Steamworks in exchange for helping her find out what happened to her little girl. However, on the way through the Steamworks, Starlo suddenly arrives with his posse to confront Ceroba, at which point she flees, leaving Clover behind.

The posse take Clover back to the Wild East, where it's revealed that Ceroba had actually planned to take Clover's Soul to finish her late husband's research project, which specifically requires a human soul untainted by violence. After learning this, Clover, Martlet, and Starlo go to confront Ceroba in the capital city. Despite attempts to reason with her, she knocks out both Martlet and Starlo with one hit each, and repeatedly attacks Clover, who endures. Realizing that she can't defeat a human in single combat, Ceroba unleashes her full power, transforming herself, and acts as the final boss of the Pacifist Route.

Despite the power of her transformation, Clover gradually wears her down, and demonstrates a hidden power of his own: telepathy. Using this ability, he reads her mind and discovers that Ceroba herself was responsible for Kanako's illness: she used her daughter as a test subject in the very research project she intends to use Clover's Soul to complete, causing her to fall into a terminal coma.

Upon her defeat, Ceroba is forced to confront the truth that she essentially killed her own daughter and tried to murder another innocent child to undo her mistakes. She breaks down from the guilt, and asks Clover to kill her for what she's done, allowing the player the choice to either execute her or spare her life before they move on to Asgore.