Mei Hatsume, the girl from support course, had made a time-travel portal and decided Class 1-A would be the perfect people to test it on.

Class 1-A entered and everything looked normal, however as they entered their classroom, it was filled with other students. The weird part was that they looked just like them. The students looked like another version of them, like they were their children in the future. Of course they were, it was a time travel after all