A large typhoon once every few years. Let's go home early today ... I thought so, but when I realized it, it was the usual time. The train was suspended ... the road was flooded ... I ended up staying at school. That was the time. "Teacher ... What are you doing until this time?" Utsumi, a student, was also left behind at school. A dangerous and nasty night was about to begin, alone in a large school building until morning.