Nobody knows what this OVA is about while watching it. That's the entire point. The protagonist wakes into a collapsing world where the people he remembers stop existing mid-conversation, where reality fractures without explanation, and Aya is the only constant in a place designed to unmake itself. You're not solving a mystery. You're watching someone realize that knowing the truth might be worse than the comfortable unreality he's been living in. This is the kind of three-episode OVA that trusts you to sit with dread instead of answers.

A high school student with no given name spends his days with three friends, dozing in class and singing karaoke after school, but his nights are full of nightmares about death and disaster. He notices that his memories of people and events don't match what his friends remember, and he starts glimpsing things no one else can see. One evening the group trails a shadow with no one casting it and runs into a crowd of zombies. His search leads him to a mysterious girl named Aya, and with her help he comes to suspect that his world may not be real and that many people he knows may no longer exist. The three-episode OVA mixes horror, mystery and science fiction.