In Mask Girl, Kim Chun-ae, Mo-mi’s best friend, tries to mislead Kyung-ja by pretending to work with her to find Mo-mi. Kim Sang-ji and Han Jae-yi play the role of Kim Chun-ae.
Kyung-ja, who wants to kill Mo-mi and get revenge for her son’s death, finds Kim Chun-ae with the help of one of Mask Girl’s fans. She kidnaps Chun-ae and tries to kill her, as she believes that Chun-ae is Mo-mi.
However, Chun-ae tells her that she knows who Mask Girl is and that she can help her find her. As Chun-ae claims to hate Mo-mi just as much as Kyung-ja, the two women join hands to look for their common enemy.
When Chun-ae was in school, she was a painfully shy student. Due to this, she did not fit in with others. There was a boy in her class named Bu-yong, who was training to be a K-pop idol. He was Chun-ae’s first love, but Chun-ae could never talk to him.
Sometime later, Chun-ae met him again, and Bu-yong took advantage of her feelings. He would often borrow money from her and never return it. Bu-yong eventually became an idol and started ignoring her.
Chun-ae then found out that Bu-yong never saw her as anything other than his bank account. A scorned Chun-ae exposed Bu-yong’s misdeeds, and Bu-yong was forced to leave his band. His career was ruined forever. On the other hand, Chun-ae got plastic surgery to become beautiful.
Years later, Chun-ae runs into Bu-yong again. She falls in love with Bu-yong, who is unemployed. She pities him, so she asks him to stay with her while he looks for a job. She soon realizes that it was a mistake to do that, as Bu-yong makes no effort to look for a job or do household chores and leeches off her.
To provide for both of them, Chun-ae starts working as a dancer at a nightclub and becomes the club’s star. That changes when Mo-mi gets a job there. She steals Chun-ae’s clients as well as the spotlight.
When the two women get into a physical fight one day, Chun-ae gets her hands on Mo-mi’s necklace, the same necklace that Mask Girl used to wear. When Kyung-ja sees her wearing that necklace, she thinks Chun-ae is Mask Girl.
However, Chun-ae tells Kyung-ja the story of her life and tells her that she wants to work with Kyung-ja, as she wants Mo-mi gone. Kyung-ja believes Chun-ae and allows her to aid her in her search for Mo-mi.
While most of Chun-ae’s story is true, the fact that she hates Mo-mi and wants her dead is not. The truth is that Mo-mi is like a sister to Chun-ae. They never fought for the spotlight at work; the two women shared it.
Their past and their pain connected them. Furthermore, Chun-ae did not steal Mo-mi’s necklace; Mo-mi gave it to her herself. In fact, Mo-mi told her everything about her past, including the fact that she has committed murder, and Chun-ae decided to protect her.
So when she realizes that Kyung-ja wants to kill Mo-mi, she makes up a story about their rivalry and wins Kyung-ja’s trust. She then warns Mo-mi and asks her to run away. At the same time, Chun-ae asks Bu-yong to vacate her apartment.
She realizes that Bu-yong knows that she is the one who exposed him and ruined his career. He refuses to leave and beats her up. Chun-ae then decides to run away with Mo-mi. Before leaving, the two women stop at Chun-ae’s apartment, and Chun-ae goes inside to get her jewelry.
Bu-yong catches her trying to run away and almost kills her, but Mo-mi comes to her rescue. Bu-yong hurts both women, and they end up killing Bu-yong together. Meanwhile, Kyung-ja finds out that Chun-ae lied to her and follows her and Mo-mi.
While leaving the city, Mo-mi and Chun-ae stop to dispose of Bu-yong’s body, and an armed Kyung-ja corners them. Mo-mi had told Chun-ae about her pregnancy, so Chun-ae tries to protect her once again by telling Kyung-ja that she is Mo-mi.
Kyung-ja decides to kill both of them. They try to snatch the gun from Kyung-ja, and Chun-ae gets shot in the process. In her final moments, Chun-ae hits Kyung-ja with a rock to save Mo-mi’s life. Chun-ae dies trying to save her best friend, who is left heartbroken and alone once again.
Also Read: Ju Oh-nam: Mask Girl character explained