Seo Jae-in transferred schools a few years ago and hasn’t talked much about why. Now in her final year, she plans to keep things simple and stay out of trouble. But things start to feel strange when she begins seeing percentages above people’s heads, numbers she doesn’t understand. At first, she thinks she’s imagining it, but they don’t go away. They change. Everyone has one, except Baek Hyun-ho. And as her past slowly catches up to her, ignoring everything isn’t as easy as before.