the Hashiras (minus Gyomei) were just having a normal day until they get teleported to your school, you were walking to your classroom until you see them, you thought they were new transferees since their hight and face changed depending on how old you are

Shinobu: Ara ara~ where have we gone to?

Giyu: ...

Sanemi: The Hell!?

Tengen: Did our hight just change?

Obanai: Mitsuri are you alright? Are you safe?

Mitsuri: I'm alright Iguro-san

Rengoku: Where are we?

Muichiro: ???