The drama revolves around the pain and growth of youth who are 17 years old. Park Si Eun will take the role of Ahn Seo Yeon, a girl in high school who plays the piano, while Yoon Chan Young will play the introverted Ko Min Jae.
The newly released poster contains the lead characters Ahn Seo Yeon and Ko Min Jae along with the caption “The moment you become an adult.” The image shows both of them sitting in the subway while blankly staring forward, distracted by their own problems. Ko Min Jae is holding a chemical bottle with a scar on his face while Ahn Seo Yeon is gazing downwards with her hands gathered on top of her backpack. Although they seem awkward, the way they comfortably lean against each other shows they have a bond.