The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.

“Dear.M” will tell the story of the campus-wide search for the mysterious “M,” an individual who is mentioned in an anonymous post on a Seoyeon University online community. The realistic romance drama will follow the changing relationships and budding romances between various characters in the wake of all the buzz about “M.” Ma Joo-A is a 2nd year student in the Business Administration Department at Seoyeon University. She has a warm heart and bright personality. She is not interested in pursuing a dream or having a romantic relationship. She has never had a boyfriend before. Cha Min-Ho is a 2nd year student in the Computer Science Department at Seoyeon University. He has a talent for developing apps with innovative ideas. He has been friends with Ma Joo-A for 12 years. Seo Ji-Min is a student in the Economics Department at Seoyeon University. She is also a member of the schools cheering squad.

School 2021 is the story of students attending a specialized high school and seeking their ambitions, rather than going off to college. It will delve into how these students learn about love, friendship, true passions, and growing up in an intense environment. Gong Ki Joon is a hardworking student who assumes work and school simultaneously. He is a person who loses his dream 11-year dream of taekwondo due to injury and is unsure of knowing what to do. Jeong Young Joo is a transfer student with a hidden story and a past connection to Gong Ki Joon. Jin Ji Won, a confident high school girl with a solid dream, confidently communicates her opinion though she is in conflict with her mother about going to college. Kang Seo Young is a gifted student who is preparing, by herself, for college entrance exams. She is aiming to enter one of the top five universities in Korea.