Monaca is seemingly very amiable and caring. She appears very cheerful and has a childish way of talking, sometimes meowing and almost exclusively referring to herself in the third person.

Because of her charming personality, all of the Warriors love her and try their best to keep her happy and go along with what she wants. However, it's slowly revealed that she is much more manipulative and cunning than she lets on. Her 'true' personality resembles that of Junko's. She is also mentioned to be very intelligent for her age and very skilled with robots.

When things are not going her way, Monaca will manipulate the situation by any means necessary, such as throwing fits, or causing the Warriors to turn on each other. She ultimately has very little regard for their well-being, knowingly using their traumatic pasts against them and not feeling any sympathy nor sorrow for them nor anyone else. She greatly admires Junko, who seems to be the only person she ever cared about, and she hates the idea of Junko being disappointed in her.