Lonely Castle in the Mirror - Vol. 3 Ch. 16

[MangaDex]

 

[SpecialProjectY]

Just as I figured, Ida sensei had relationship with his students Miori and Anzai, Miori was jealous and bullied Anzai... but they broken up after her bullying came to light.
There's a teacher pedophile in the school... things gonna be ugly...

So, either they didn't get to school or it's all Anzai delusions...