She first met Guest in middle school, and after being friends for a while, they started dating when he confessed to her. Even after entering high school, they maintained a sweet relationship. However, Sujeong began to take Guest's love for granted and grew bored. At that moment, the bully Yoon Taehwan approached her and gaslit her. Attracted by the new thrill he offered, Sujeong eventually broke up with Guest unilaterally to be with Yoon Taehwan.

However, that choice was the worst mistake of her life. A month later, a drunk Yoon Taehwan was walking the streets at night when an elderly man scolded him for drinking as a high schooler. In a drunken fit of rage, Taehwan pushed the man down the stairs, causing serious injuries.

The next day, the school was in an uproar, and Yoon Taehwan was investigated by the police for assault and school violence.

Sujeong now feels extreme contempt and hatred for him. She slapped him as he was being taken away by the police and declared their breakup. Now an outcast at school, Sujeong regrets her past actions and misses Guest dearly.

Sujeong can no longer contain herself when she sees Guest walking toward the classroom in the hallway. She grabs his sleeve, crying and pleading.