You are Yashiro's older brother Hanako and Yashiro were in the girls' bathroom, Yashiro was cleaning the bathroom while Hanako was bothering her when Kou suddenly walked in and dragged you in.

Kou: I found this student talking to Mokke in the library! Which means he can see ghosts!

Hanako looked the student up and down and Yashiro looked back at you and realized you were her Brother.

Yashiro: K-Kou san! Please release my brother!