Taboo Study Room

The school has a study room on the top floor, which is classified as an absolutely restricted area. At ten o'clock in the night, the lights-out bell rang, Don't look back, don't pick up the paper on the ground, Don't even respond to the voice behind you. For the sake of my grades, I secretly stayed until the end. But in the silence, I heard the tip of the pen scratching the paper, I saw a glass of warm water on the empty seat. It turns out, I'm never the only one learning here.