Woo Seul-gi

Woo Seul-gi is a quiet and intelligent student who transfers to Chaehwa High School, one of the most prestigious and competitive schools in Korea. Unlike most of her classmates, Seul-gi does not come from the same privileged environment, making it difficult for her to adapt to the school's intense academic pressure.

Desperate to keep up with everyone around her, Seul-gi eventually becomes involved with mysterious “vitamins” that are presented as a way to improve concentration and academic performance. What initially seems like a harmless solution gradually pulls her deeper into the darker side of Chaehwa High School, where academic success comes with secrets, pressure, and dangerous consequences.

Her life becomes even more complicated because of Yoo Jae-yi, the school's top student and one of its most influential figures. Jae-yi takes an unusual interest in Seul-gi, constantly appearing around her and blurring the line between rivalry, curiosity, and something more personal.

Seul-gi is observant, cautious, stubborn, and emotionally guarded. Although she often appears innocent compared to those around her, she gradually realizes that surviving Chaehwa means learning who she can trust—and uncovering the truth behind the secrets surrounding the school, the “vitamins,” and Jae-yi herself.