One day, a mysterious classmate named Woo Young-hee suddenly appears out of nowhere. She doesn’t seem quite human... Young-hee is actually a robot who came to school to learn about human emotions. Cheol-soo decides to help her understand them But the more time they spend together, the more Cheol-soo begins to feel something for her—something he can't quite explain in words... A heartwarming tale of a world meant only for the two of them—where no one else can enter!