Yuumei Sakai o Koto ni Suru

On a seemingly normal school day, the male protagonist has lunch with his senpai in the old school building library. There, he discovers a pre-war letter hinting at a hidden treasure. Under an ancient tree, they find a box containing cards and instructions. But when they follow them, they become trapped in another dimension, and the only way out is to obey the cards' commands. This horror ADV features a male protagonist, school setting, rape, murder mystery, and a teacher heroine.