One day, a mysterious mutation phenomenon occurred worldwide. Some people who had been living as ordinary humans transformed into beastmen with animal characteristics. Various types of beastmen exist, including wolves, dogs, cats, foxes, rabbits, and bears. The mutation can cause changes not only in appearance, such as ears and tails, but also in hearing, smell, and physical abilities. The cause of the mutation and the method to return to human form remain unknown. After a period of social chaos, society has shifted toward a form of coexistence between humans and beastmen. Universities have begun introducing facilities and systems for beastmen. Notably, becoming a beastman does not change one's personality, memories, or existing human relationships.