- 2NE1 Sandara Park as Teacher Dara
- CNBLUE Minhyuk as Minhyuk
- CNBLUE Jungshin as Jungshin
- SNSD Seohyun as Seohyun
- B1A4 Shinwoo as Shinwoo
- B1A4 Jinyoung as Jinyoung
- MissA Suzy as Suzy
Other Cast: 2NE1 Minji, Bigbang Seungri, Shinee Taemin, Bigbang TOP
Sungkyunkwan High School recently became a co-ed school. Since the female student’s population was still a minority, the school administration brought in female teachers to correlate with the female students.
Dara – A fresh university graduate who will be teaching for the first time in High School. She has had no experience in teaching yet aside from her practicum during her university years. She’s very excited to handle her first class. Since she looks young, students mistake her for a student. She tries to uplift her image by putting on eyeglasses and projects a stern look. Still, she has a hard time dealing with her students.
Jungshin – an outgoing happy go-lucky senior student who is the Student Organization President and the most popular guy in school especially with girls. He loves to make bets with his friends especially with his childhood friend Minhyuk to keep his own self motivated. Though he is popular and labeled as a playboy, he has a dark secret which he is afraid to tell anyone and only Dara knows his secret.
Minhyuk – a smart senior student who is also very popular with girls but very shy around them. He treats Jungshin as his best friend and his defense from girls. He comes from a well-off family and his father expects him to soon run their family business. But he loves to play drums and dreams to be part of a band. He shares this sentiment with his teacher, Dara.
Seohyun – an intelligent naïve junior student who has a long-time crush on Minhyuk. She likes to follow Minhyuk around and sits with him at the library without ever talking to him. She has no dreams except to be with Minhyuk. She’s contented with just staring at Minhyuk until she becomes jealous of their teacher Dara whom Minhyuk spends a lot of time with.
Jinyoung – a transfer junior student who is known for his outspoken attitude which gets him into trouble occasionally. He transferred to Sungkyunkwan highschool because of female minority population. His mother left them for another man when he was very young and grew up with hate for women. Thus, he loves to bully girls especially Suzy and their teacher Dara.
Suzy – a popular junior student who is known for her talents in performing arts and have lots of male followers. A certified heart-breaker, she enjoys dumping guys because it’s her way of revenge. She lives with her un-wed mother who gets to live with different guys from time to time. She has a strong personality outside, but very soft and weak inside. Shinwoo is her ally against Jinyoung who loves to bully her around.
Shinwoo – a senior transfer student and is also a childhood friend of Suzy. He grew up with Suzy on the same neighborhood and knows about her difficulties in life. He purposely transferred to this school to be with Suzy and protect her. He became popular in school when he sang and danced with Suzy during a school activity. Then suddenly, he met her again, his tutor who is also his first love.