Nagisa is a typical schoolgirl who often wakes up late, rushes to school, and meets up with her friends along the way. One morning, she encounters a woman in an odd uniform who gives her an unnerving stare. Later that day, while gazing out of the window, Nagisa notices a ball that seems to bounce on its own. The ball flies toward her window seat, shattering the glass, yet she remains unharmed. When she turns back to the front of the classroom, she sees a gaping mouth with teeth inches from her face, and no one else is present. She screams, and the scene suddenly returns to normal, with her standing in the middle of her class, now the center of everyone's curiosity. The cause of her scream remains a mystery.