>>530069340
>It's seen as normal in their world
It's confirmed there are no other sensei's in this world, and Mika says most students go their entire school life without ever seeing a sensei. All their classes are books on tape and workbooks, which are the ascension items you use to level up student skills. The classes are 99% self study and 1% guest lecturer
Sensei says it's his job on this world without adults to be the adult all the kids need that they've never had before. In this world of children he exists to be the one adult who has chosen to help them, and guide them. It's kinda the entire point of the game, the role of an adult and the duty of an adult. It takes the allegory to an extreme with a world of nothing but children who distrust and hate adults, he exists to help them one by one. Sensei's role is to be "the good adult", he sets an example of what it means to be an adult.