Isaku

Kenta is an ordinary Japanese teenager who enjoys his high school life. One day, he receives an anonymous letter, apparently from a girl, who says she likes him, and wants to meet him in an abandoned school building. However, upon arriving there, he finds that several of his classmates and teachers (mostly female) are there as well. When Kenta realizes they were lured there, it is already too late - they are locked in the building, unable to get out.