It is said that Class 1, a senior class, has never changed any students. It has been a hundred years since the establishment of Eskar School. No matter how much time has passed, the 40 people in that class have never changed. This is surprising, and it also makes many people speculate that they are not human beings, until in the end they discover that there is indeed no one in that entire class.
Premise: This is a prosperous era a hundred years after the protagonists' experiences. From the perspective of the supporting characters, we gradually understand what the protagonists experienced back then. The protagonists may not appear until later.
Intention: Young people should be high-spirited