The inhabitants of this world can switch between human and beast forms. Everyone is born into one of two categories: "beautiful human/ugly beast" or "ugly human/beautiful beast."

Life is functional in either form. Whether one is a mouse or an elephant, mystical forces ensure that they can navigate most situations without issue. However, physical limitations still apply—a mouse cannot wear clothes designed for a human.

Body size in beast form is comparable to the human form. A 170cm tall person would be about 1m tall as a mouse, and just under 2m at the shoulder as an elephant.