Three years ago, global warming was not so serious. The little penguins in Antarctica were jumping around in the ice and snow every day without worrying about melting glaciers. Summer in the north is never as sticky as in the south. A gentle breeze blows through the clothes of pedestrians, and the coolness takes away the anxiety of summer. Today is the day for the new students of Longhua Middle School to register, and it is also the day when their story begins.