Season 1
Kim Yoon Hee is a smart, responsible young woman with an independent drive. Since her father passed away, she has worked to support her family, but also managed to do well in her studies. When her younger brother's illness worsens, and their family is in danger of being evicted from their house for lack of money. In her desperation to support him, Yoon Hee decides to take the men's only national exam under her younger brother's name and disguises herself as a boy. On the day of the exam, Yoon Hee meets Lee Seon Joon and becomes friends. Lee Seon Joon comes from a privileged background and also possesses good looks. He is also arrogant. They both pass the national exam, and she has to share a room together with him at Sungkyunkwan University, while hiding her true nature. There, she becomes friends with the playboy, Goo Yong Ha, and rebellious Moon Jae Shin.
01. Lesson 1
In order to make money for her family, Kim Yoon Hee takes tests and creates cheat sheets for lazy scholars, bringing her face to face with the upright Seon Joon.
02. Lesson 2
Seon Joon challenges her to take the entrance exam for the all-boys school Sungkyunkwan University, not knowing that she is a girl in disguise.
03. Lesson 3
Politics and discrimination enter Sungkyunkwan as Ha In Soo pressures Seon Joon to live in the Western dormitories with the rest of his political faction.
04. Lesson 4
In Soo underestimates the loyalty Seon Joon and Yoon Hee have for each other. An archery competition brings about startling consequences for Yoon Hee.
05. Lesson 5
Professor Jung discovers Yoon Hee's true identity and leaves her unnerved. She faces the threat of expulsion and the unspeakable charge of offending her family and the king.
06. Lesson 6
Yoon Hee's fellow Sungkyunkwan scholars rally behind her as she trains in earnest for the Archery Competition.
07. Lesson 7
The day of the Archery Competition has finally arrived. Much is at stake for Yoon Hee, whose very fate at Sungkyunkwan will be determined by the match's outcome.
08. Lesson 8
Sungkyunkwan scholars are permitted to visit home during break. Meanwhile, suspicions continue to arise regarding Yoon Hee's true gender and identity.
09. Lesson 9
The scholars return to Sungkyunkwan from their break, and there is already trouble. A thief has stolen several valuables, and Yoon Hee is accused of being the culprit.
10. Lesson 10
Yoon Hee and her Sungkyunkwan friends set out to find the elusive thief. They are surprised to discover, however, that the person behind the robberies is not the criminal they expect.
11. Lesson 11
The Red Messenger continues to wreak havoc while the king makes a decision that rattles the political factions. Yong Ha schemes to bring Yoon Hee and Seon Joon together.
12. Lesson 12
It's Open House at Sungkyunkwan, and visitors swarm its campus. The hunt for the Red Messenger continues to intensify while Seon Joon grapples with his attraction to Yoon Hee.
13. Lesson 13
Jae Shin and Seon Joon's competing affections for Yoon Hee intensify during a sports match. The fake Red Messenger continues to cause trouble.
14. Lesson 14
In Soo becomes increasingly adamant in discovering the Red Messenger's true identity. Rumors of intimacy between Jae Shin and Yoon Hee spread throughout Sungkyunkwan.
15. Lesson 15
Seon Joon's engagement to Hyo Eun weighs on his mind as he grapples with his attraction to Yoon Hee, who he still believes to be a man.
16. Lesson 16
While the Sungkyunkwan scholars prepare for a schoolwide exam, Seon Joon and Yoon Hee's relationship continues to develop.
17. Lesson 17
The Jal Geum Quartet is summoned by the King to solve a political mystery that brings about shocking revelations from the past.
18. Lesson 18
Seon Joon and Yoon Hee's relationship is threatened with heartbreak when they discover the truth concerning the death of Yoon Hee's father.
19. Lesson 19
The hunt for the Red Messenger becomes more intense, and Lee Seon Joon makes a self-sacrificing decision that affects the other three friends.
20. Lesson 20
Chaos erupts within Sungkyunkwan when Ha In Soo finds out that Kim Yoon Shik is really a girl.