The makura gaeshi or pillow flipper, was thought to cause kanashibari–sleep paralysis. It happens when you believe you’ve woken up in bed, but you’re actually somewhere between wakefulness and sleep. You’re aware of the room around you, but there’s a subtle change in the air. You try to move, but you’re frozen. You try to call out, but you can’t make a sound. It’s a terrifying experience.