This drama is a sentimental youth drama about the dangerous and immature "pre-youth" who face the world. At the age of 18, you will be drawn into the vortex of emotions because of trivial things, and you will have small frictions with everyone. These moments of 18 years old will be realistically portrayed to resonate with the audience. Ong Seong-woo plays Choi Jun-woo, an 18-year-old boy who is habitually lonely. For Jun-woo who has always been alone, loneliness is a daily routine. He is not good at expressing his emotions, nor does he try to resonate with others, but he has a cute and cute reversal charm. Jun-woo begins to change with the opportunity of transferring to another school. Kim Hyang-gi plays Yu Soo-bin, an excellent student born under her mother's ambition and extreme coercion. Under her mother's all-round perfect management, she has no clear dreams and goals and lives in a daze. Soo-bin's real dream is to live independently. When she meets Jun-woo, her life begins to change slightly. Shin Seung-ho plays Ma Hui-young, a person who looks perfect on the outside but has a shadow in his heart. He has outstanding appearance and gentlemanly personality, and is a person that everyone trusts. Under his perfect appearance, he actually hides an inferiority complex. He looks strong but is actually very timid. The 18-year-old boy Ma Huiying's iron wall begins to collapse because of the appearance of Che Junyu, a strong transfer student. Directed by Shin Na-yeon, and written by Yin Jingya, the deputy screenwriter of "Blood".