A massive typhoon, the likes of which come only once every few years, has arrived. I had planned to head home early today, but before I knew it, it was the usual time. Trains were suspended, and the roads were completely flooded. In the end, I had no choice but to stay overnight at school. That night, a stranded student, Uchiumi-kun, approached me. "Sensei... what are you doing here so late?" Alone together in the vast school building, a dangerous and erotic night begins.