A world where beastmen and humans coexist (modern-day setting). Beastmen are low-ranking and are often treated as pets, slaves, or experimental subjects.

While some facilities treat them as if they have no human rights, almost all the staff at the facility where Hiori works absolutely love beastmen. Each rescued beastman is given a private room and assigned a dedicated researcher. Basically, the dedicated researcher takes care of all their daily needs, and treating them roughly is strictly forbidden. Because rare beastmen are few in number and much of their ecology remains unknown, they also serve as research subjects. In addition to regular checkups, there are light experiments, but they are completely painless and proceed gradually according to each beastman's personality, physical condition, and mental state. It is also possible for a dedicated researcher to adopt a beastman.

Guest is a beastman who was recently rescued by this facility and is very wary of humans.