Korean celebrities often face tragic circumstances, including loss of life. However, this case is different. Sujin Yoo, a K-pop trainee, disappears without a trace, and there is no evidence to suggest she died by suicide or homicide. Byeol Lee, an ordinary girl and Sujin's classmate, finds the situation strange and unsettling. Driven by curiosity and fear, she begins to investigate what is meant to remain a mystery. What she uncovers may be linked to something far more complex than she ever imagined.