Why is the teacher attacking the students, when she just talked to her and found out that it isn't what she was imagining?
Does the teacher have bipolar in the insanity scale?
@Milanin if I had to take a wild guess based on her little monologue at the end, I would say she might be/be possessed by an Amanojaku: a kind of oni that does (often very nasty or perverse) stuff just to be contrary to reason and expectation.
Honestly before that reveal I was of the firm belief that some sport of sex crazed ghost Or invisible thing was going Down deep In the mouths of those people.