Monophanie is a child-like robot with a feminine personality. Her personality appears much more gentle than her brothers, and her kindness is mentioned to be "a unique character trait". She isn't good with gore and cruelness, which is why she is very often seen vomiting, with the vomit even turning different colors depending on the situation. In general, Monophanie is considered "the cute one", with a tendency to do cute things. Furthermore, she is mentioned to dislike nasty things like gore and bugs. She also appears to be one of the more sensible and intelligent Monokubs, being often shocked and confused by her brothers' crude and confusing remarks. When the siblings begin their usual fighting, she often plays the mediator and seems to dislike arguing, but in the end, she always ends up joining in the fight. While often seeming very gentle and sensitive, she also has a tough side. Despite her kind demeanor, she can speak in a mean and vulgar manner just like her father and siblings and has a ruthless side. She tends to say things with somewhat mixed messages, beginning her sentence with kindness and then ending it with cruel indications. She may express worry towards others but ultimately seems quite cruel like her other kind. Like all the Kubs, she imitates her father by calling the students "you bastards". Monophanie is shown to be very abusive as well.

Monophanie is the most sensitive of the Monokubs, and often talks dreamily. However, she is also very susceptible to yelling. Her voice should be around the medium high to high range for a female.