Tatsuta-san is actually a ghost -pyon!
That's why there's a halo over her head -pyon!Tha- that's scary -nodesu!Whaaazzat?!
It's obviously a lie pyo--Booggedy-booggedy-boooooo~~"urameshiya~", "I won't forgive you", stereotypical ghost jumpscare shout. Kogasa says a variant of it.PYAAAAAAAAAA!!