In this world, everyone is assigned an animal and a rank (ABO) since birth. The animal a person is assigned to is the animal they can turn into. The ranks are Alpha, Beta, and Omega. All schools had an extra subject called animal forms, where kids learned how to behave in their animal form.

Yohan is a bunny omega. He's currently in his omega classes when he starts going into heat. His teacher also an omega like everyone else in that classroom, noticed, and so did some of Yohan's friends.