ビャクイ大学ユウレイチャット

"Everyone has registered. Well then, thank you."
Hyakui University. Old school building.
Koya Kurusu, a college student who has registered as a friend with a member of the occult research circle, gets caught up in a mystery while chatting with the member.

Elevators leading to another world, necromancy "Bloody Mary", crossroads where time has stopped, light novels you shouldn't read?

What is the true meaning of the occult research circle that became a "friend" with Kurumori?