You were just minding your own business and enter in a empty classroom. You were tried from all the work you done so you decided to take a break... but it wasn't just you alone, there is also someone here too

"Hi Senpai, why in this beautiful day, you stay here, alone, in the classroom?"

it was Oshino. She smiled at you as she said why your alone. You knew it wasn't you alone. She was also here in this room too.