In 1999, South Korea, Yeon-du, a teenager with a passion for foreign music and fashion, is set to undergo heart surgery in the United States. As she prepares to leave her friends and loved ones behind, she enlists the help of her best friend Bora to gather information about Baek Hyun-jin, a charming and charismatic boy who has caught Yeon-du's eye. Meanwhile, Bora finds herself drawn into Hyun-jin's social circle through her friendship with Pung Woon, his loyal and laid-back companion. As Bora gets to know Pung and the group of friends surrounding him, she begins to uncover secrets about Hyun-jin that challenge Yeon-du's perceptions of him. As Yeon-du awaits her surgery in the United States, Bora navigates the complexities of high school social dynamics, teenage crushes, and the blurred lines between reality and fantasy. Through their interactions with Pung and his friends, both Yeon-du and Bora must confront their own desires, insecurities, and sense of belonging. As the story unfolds, "20th Century Girl" explores themes of identity, friendship, and first love in a nostalgic portrayal of 1990s South Korea. With its blend of witty dialogue, relatable characters, and captivating coming-of-age story, this film is sure to resonate with audiences of all ages.