Lee Yoon (played by Park Bo Gum) is the eldest son of the 23rd emperor of Korea. He’s indifferent and picky. He’s been dealing with national affairs on behalf of his sick father since 19 years old. Hong Le Yun (played by Kim You Jung) was dressed and raised as a boy since her childhood. At her age of eight, she was separated from her mother. When she grows up, she earns money by writing love letters and analyzing love strategies for others. Lee Yoon goes out of the imperial palace to meet the man who wrote love letters to his sister, but the one he meets is “Hong San Kook” disguised by Hong Le Yun. They know one another because of the misunderstanding. Hong San Kook is sold to the imperial palace to be a eunuch unexpectedly and she knows Lee Yoon is the crown prince. Lee Yoon tries his utmost to torture Eunuch Hong but he finds he’s getting to love the man more....

Kim So-Hyun, Nam Ju Hyuk and a member of BTOB, Yuk Seong Jae were chosen as new stars of next generation who can start a school craze and the leading roles of the 6th drama of KBS’s unbeaten myth, “School” series. This drama tells a school story, the heroine tried to commit suicide due to her classmate’s malicious bullying, but ended up losing memory. Accidently, she inherited the identity of her twin sister and started to search for the truth....