Despite being the youngest of the slime sisters, MEDUSA also appears to be the most mature and practical. Calm and collected, she rarely lashes out and is shown to be extremely patient, demonstrated as how she tolerated much of SWEETHEART's complaints and how, according to her FOE FACTS entry, she is skilled at calming down her other two sisters whenever they argue. However, she does not like people with bad manners and feels they should be taught a lesson. She often addresses people as "doll". She loves everything pretty, experimenting with liquid elements as she believes they are just that and being horrified and unusually emotional when her furniture is ruined. She also loves pretty boys, appearing attracted to HERO and wanting to keep him to herself because he is "too pretty to sell." Her superficial personality is further shown after she recreates her destroyed body, marveling over her own gorgeous body and laughing mischievously while pointing out that she gave herself some "minor improvements," likely referring to her chest size. She also mischievously gives OMORI a MYSTERY POTION, claiming it has "entertaining" results, and it ends up temporarily transforming him into a girl when used underwater. During her more mischievous and suggestive moments, MEDUSA lets out a "kukuku" laugh. Out of the three siblings, MEDUSA seems the most skilled as a scientist due to her focused personality. When creating PERFECTHEART, she does not make mistakes in the process unlike her sisters, and the only reason her experiment is shunned by SWEETHEART is because SWEETHEART herself was intimidated by the perfection of the project. The HUMPHREY working for her pride themselves as being the best of the best and appear to be more refined than the ones who work for her siblings, as they do not often complain about their working conditions and are shown to possess more high-level thinking abilities. Unlike her sisters, she doesn't mistreat her workers and never yells at them, but the way she'll pace back and forth when she's mad is frightening to them regardless. Her HUMPHREY workers are also allowed to play games and relax.