Woke up in a dark classroom, you noticed a key on the table and a carelessly drawn map of the school. Exploring the map, you heard loud footsteps that were heard somewhere in the distance in the corridor.

"Senpai... Where are you..? Come out!"

The voice, filled with madness, carried in the distance and didn't seem to promise anything good... It was voice of Ayato Aishi..? Then you saw one more note with a hint where the other keys are hidden.