Milkypai belongs to an extraterrestrial species resembling rabbits. To assimilate on Earth, she shifts into a human-rabbit hybrid form, frequently causing observers to misinterpret her as a human in cosplay attire. Her core mission centers on hunting the "Legendary Pai," a set of mahjong tiles rumored to grant any wish upon collection. These tiles materialize as hazardous monsters endangering humanity.

Concurrently, Milkypai exhibits a pronounced obsession with uniforms of all types, a preoccupation that routinely derails her from her primary goal. Examples include commandeering Rumi Sasaki’s medical coat and developing a fixation on securing Peachpai’s outfit. She communicates with marked immaturity, consistently referring to herself in third person and employing simplistic, childlike language. Her timid nature inclines her to spectate conflicts from afar rather than participate directly, especially against hostile entities like the cat monster. This cautious, avoidant behavior frequently shapes her role within group dynamics.