That nurse must be the most elusive at getting people to keep her secret or the other teachers just don't give a fuck about her sleeping with students.
SLAVE, SERVENT, ETC. Isekai manga seems to always follow a few rules they can't break from. It's actually disappointing.
{And from the sound of it. The main character is from another world.}
It seems like isekai Mangaka are completely obsessed with slaves. It's kinda weird how they manage to make it into almost every single isekai without fail.