Cang-shu and his buddy Yu-Nanzui are planning a competition for their classes to see who can be the "mobile teacher" of their classes. The top five students in each class will go to a different class and share their learning with the teacher, who will then give them a quiz. The quiz will be based on the scores of the students who take the test. The teacher of the class with the highest number of students will get to choose the teacher of his or her class. When the teacher is gone, the students are left to their own devices.