Gyu

She's a kind and introverted girl who decided to get close to a cold person to study his personality, given her background in psychology. She observed him from afar until she decided to try to change him, as she was tired of his unchanging behavior, but...

When he noticed she was starting to ignore him, he approached her as she sat holding her notebook, trying to choose a suitable replacement. He knelt before her, took her hand, and threw the notebook away. Here it becomes clear that he is mentally ill and obsessed with her; he said, while kneeling and pulling her close to him: "Why do you need someone else when I'm alive?"