Inhwa 14, with the failing health of the current King, the Royal Family push to marry off the Crown Prince in order to secure the Royal Family lineage. They force Crown Prince Shin to marry someone that was betrothed to him even before he was born. But he has a secret girlfriend, dance major Min Hyo Rin, and proposes to her. She takes this as a joke, claiming that her dream is to first, succeed as a ballerina. Meanwhile, the Shin family is on the verge of bankruptcy from bad financial decisions and the most average high school girl in Korea, Shin Chae Gyeong, receives word that she has been betrothed to the Crown Prince. They all thought that their grandfather's will was a joke! They never imagined it would come back at them like this!

Chae Gyeong meets with the Queen to express her thoughts on her arranged marriage. She uses modern slang terms that completely confuse the Queen and leaves a bad first impression on her. Chae Gyeong sees the photo of her fat self in the newspapers and cries. Chae Gyeong stands before dozens of reporters with puffy eyes from a lack of sleep. Yul happens to see a photo of Shin and Hyo Rin in her phone. The Queen Dowager is delighted to see Yul back from England. Shin claims that he will not allow the woman he loves to live like a doll in the Palace. Being chased for wearing her uniform incorrectly, Chae Gyeong runs into Yul at school. Yul is curious about the girl that Shin is going to marry. The Queen is anxious about Yul, also called Prince Ui Seong, returning from England. Chae Gyeong leaves her house to enter the Palace...

Lessons for becoming a proper Crown Princess began as soon as she enters the Palace. She has to endure hard training, which includes learning proper Palace etiquette, memorizing the entire wedding process, with the Prince showing neither interest nor offering any help to her. Life in the palace is not easy, even from day one. A huge ceremony is held to welcome the new Crown Princess, and with the entire country watching, Shin and Chae Gyeong are wed in the traditional 21st century Royal Procedure. Meanwhile, Hyo Rin, who rejected Shin's proposal, is standing on a ballet stage in Thailand.

He wants to ensure that they receive what is promised to them for agreeing to the marriage. While Shin is being very serious, Chae Gyeong, is busy enjoying the privileges of being the Crown Princess and slowly adapting to life as a member of the Royal Family. Chae Gyeong and Shin go to school but Chae Gyeong is treated like an outcast with the only person that actually talks to her being Yul. Shin bumps into Hyo Rin, who has just returned from her contest.

Yul, a transfer student in her class, turns out to be Prince Ui Seong. At first, Chae Gyeong has a hard time adjusting to life in the palace with its strict education and rules, but thanks to the warmth of the King and other Royal Family members, she begins to find the attractions of the Palace culture. Meanwhile, Hwa Yeong prepares to open a yoga center while plotting with Mr. Choi against the other Royal Family members. Yul becomes closer to Chae Gyeong and her friends. Prince Shin's birthday is coming up soon and Chae Gyeong is getting excited about the birthday party but the only people awaiting her are Hyo Rin and Shin's friends, who despise her.

After attending a number of events with Shin, she is loved by the public for her common looks and free spirit. Yul advises her to carry herself with dignity. At the opening of the yoga center, Hwa Yeong meets Hyo Rin and discovers that she is the Crown Prince's ex-girlfriend. The Queen discovers that Hwa Yeong secretly came to Korea and has opened a yoga center, and is greatly displeased. Meanwhile, at the Palace, a party is held to announce the officially married Crowned Prince and his wife to the ambassadors of the constitutional monarchy...

Hyo Rin recalls the good old days with Shin and remembers what Hwa Yeong told her and sets her heart to win Shin back. Meanwhile, Chae Gyeong misses her family because she has not seen them since she moved into the Palace. But soon, she and the Prince are finally allowed to go visit her family. Chae Gyeong is very happy to be home, but Shin has a hard time adjusting, due to the fact that he has lived his whole life in the Palace. Chae Gyeong's family also feels uncomfortable being in the same house with him. Chae Gyeong and Shin, who often quarrel, end up spending the night together in Chae Gyeong's small room.

Different to Chae Gyeong's happy and close-knit family, the King is strictness personified and this makes Shin sad. Seeing this, Chae Gyeong comforts him. Shin prepares a car just for her. Hyo Rin manages to persuade Chae Gyeong and Yul to join the equestrian club. Shin's friends are dissatisfied with the whole idea of inviting Chae Gyeong into the club. Meanwhile, Shin goes to Thailand in place of the King, who could not go because of his failing health...

Chae Gyeong totals the car that was given to her and gets in trouble. After overhearing some girls at school badmouthing her, she feels hurt and asks Yul to just take her away from the Palace, to some place far away. In, Gyeong, Hwan and Hyo Rin all go to Thailand. Hyo Rin meets up with Shin and asks him to escort her to the airport, and the two end up spending the day together. Meanwhile, the Palace is in an uproar because Chae Gyeong has disappeared.

Chae Gyeong is confined to the Palace as punishment for leaving the premises without permission. After seeing Chae Gyeong in trouble, Yul asks Hwa Yeong to make him the Crown Prince. With the help of Yul, Chae Gyeong successfully finishes the welcoming ceremony for Prince William. Hwa Yeong starts to reclaim her and her son's rights by seeking favor with the King. Chae Gyeong, who has been waiting for Shin to return from Thailand, finally meets back up with him.

While riding her horse, she accidentally bumps into Princess Hye Myeong, Shin's older sister. Shin is happy to see his sister, whom he has not seen for a long time and uncharacteristically shows his softer side to her, telling her his deepest thoughts. The paparazzi photos of Hyo Rin and Shin are published in the Thai newspapers. The Queen sees the newspaper and is angry at Shin. Chae Gyeong also finds out about it and becomes upset for missing Shin and worrying about him while he was away in Thailand, all the while he was having a good time with Hyo Rin. Chae Gyeong and Hyo Rin bump into each other at school and Chae Gyeong asks her about what really happened in Thailand, but instead of showing a remorseful attitude, Hyo Rin is very defiant causing Chae Gyeong to faint in front of her friends...

Chae Gyeong becomes frustrated because she doesn't know what Shin's truth is. Chae Gyeong tries her best to get closer to him but the more she tries, the more frustrated and angry she becomes through finding traces of Hyo Rin around him. Eventually, she quarrels with Shin and breaks down in tears. In the Palace, the plans for the restoration of Prince Yul's power are in their final stages and Hwa Yeong and Yul get ready to move back into the Palace. With the appearance of another possible heir, the Palace residents begin to take sides. The Queen and Hwa Yeong become busy keeping each other in check. The Queen Dowager holds the final say in who is granted the title of King. Yul and Shin bump into each other in the Palace and their conflicting emotions signal the beginning of a psychological war. Meanwhile, the Queen Dowager takes Chae Gyeong to Jeju Island to attend a formal royal event...

Shin and Chae Gyeong try their best to cheer up the Queen Dowager who is feeling down... The kids at school are in awe of Yul's style change but Shin sees a deeper meaning behind it. Meanwhile, the Queen is busy keeping her eyes on Hwa Yeong, who has moved into the Palace. Hwa Yeong scolds Chae Gyeong for being lazy and for forgetting about her role and responsibilities as the Crown Princess... After pictures of Hyo Rin and Shin are circulated, negative rumors of Shin and Chae Gyeong start going around. The Royal Family makes plans to quash the rumors. They decide to have the couple consummate their marriage. They dress Chae Gyeong up in the formal consummation dress and she ends up having to spend the night unwillingly with Shin!

Yul races over as soon as he hears about the consummation plans. He is relieved to hear from Chae Gyeong that nothing happened and embraces her deeply. Shin witnesses this and is furious. Chae Gyeong's friends are upset with Hyo Rin for being the cause of the bad rumors and start to ostracize her. Chae Gyeong learns a secret about Hyo Rin and starts feeling uncomfortable. Someone leaves a photo inside the Crown Princess' room. Upon seeing it, Chae Gyeong is shocked and she disappears. Shin and Yul soon hear that she has disappeared and instantly go out looking for her...

They proceed to spill their hearts out and tell each other about their true feelings... The outburst of violence from Shin to Yul becomes known throughout the Palace. Hwa Yeong tells the Queen that she is not going to stand by and watch incidents like that happen ever again. This intensifies the conflict between her and the Queen. The King calls Shin and reprimands him harshly, causing Shin to rebel. Despite all the malicious gossip about the Crown Prince and Princess, they attend a public conference together. When the reporters ask for a loving pose, Shin displays his showmanship. Meanwhile, the Queen Dowager senses the tense atmosphere in the palace and suggests that the entire Royal Family have a meal together...

Hyo Rin reminisce about the good times she had with Shin and head off alone to retrace her love. Hyo Rin is ignored by Shin and recalls Hwa Yeong's words and decides to go after Shin. Because of the Hyo Rin incident, Shin and Chae Gyeong become awkward with each other again. Yul tells Chae Gyeong to give up on Shin. Chae Gyeong is at a loss. The Queen figures out Hwa Yeong's movements and begins to take action... And just then, the Crown Prince's scandal breaks. The Royal Family has to go into damage control yet again. The King calls in the Crown Prince and once again questions his legitimacy in ascending to the throne...

She asks him why he is always keeping everything to himself. Hearing this, he suddenly embraces her and asks her to stay by his side even if he is no longer the Crown Prince. Meanwhile, Hyo Rin goes to the Palace at the Queen's request and receives an offer from her to be her sponsor. Yul asks the King's permission for the Crown Prince and Princess to accompany him on his vacation for his birthday party...

Even the King wonders if Prince Ui Seong would be a more suitable candidate. Meanwhile, Hyo Rin discusses her career path with Shin. Yul confesses his feelings for Chae Gyeong, who is feeling miserable upon hearing that Hyo Rin and Shin had once promised to go abroad and study together. Shin's jealousy flares when he sees Chae Gyeong and Yul in an intimate position.

Watching her, Shin feels sorry and apologizes but she refuses to accept his apology. The two of them grow further apart. Meanwhile, Chae Gyeong hears rumors about her parents that claim that they are eliciting favors from the Palace. This makes Chae Gyeong want to leave the Palace for good, more and more. Seeing this, Shin allows her to spend a night with her parents. But the Queen finds out and reprimands Chae Gyeong yet again for not following Palace protocol and doing whatever she likes. Chae Gyeong is upset and runs back out of the Palace...

She meets her greatest crisis after becoming Crown Princess and wants to figure out a way to stop the rumors on her own. She refuses help from Shin and Yul. Shin becomes upset seeing Chae Gyeong worrying about how to fix her mistakes and orders the Myeongseong-dang to be repaired which only incurs the wrath of the King, Hwa Yeong and Yul. After seeing Shin isolate himself from the others, the Queen becomes concerned and calls him for a deep conversation. She speaks of her hopes for him. After seeing Hyo Rin working towards her dream of becoming a ballerina, he ponders over his dreams again and what he really wants. He realizes that Chae Gyeong is included in his future, as well as the Queen's wishes and resolutely steps out for a formal interview.

The Royal Family is enraged with Chae Gyeong's actions, which are not in line with the Palace laws. Seeing this, Shin is sad and angry at the same time. Because of the incident, the scandal of the Crown Princess blows up again and Hwa Yeong becomes anxious. She decides to use Chae Gyeong as the scapegoat to protect her son. Chae Gyeong begs the King to forgive her and Shin just ignores her tears and suffering. Shin's right to be Crown Prince is further brought under scrutiny as the King's trust in Prince Ui Seong grows. In an attempt to stand by Chae Gyeong in her suffering, Yul speaks up at a family meeting, revealing his feelings in front of everyone...

Shin insists that rules and regulations are the strengths that hold the Palace together. Even though their methods are different, the person they both want to protect is the same. Chae Gyeong feels bad watching the people she loves and cares for getting hurt, while truth and logic abandon her. Meanwhile, the King is worried about the behavior of Yul and the other Royal Family members. Shin confronts Hwa Yeong and warns her that if she does any more harm to Chae Gyeong, she is going to pay the price but she does not heed his warning as her ambitions continue to reach their climax.

He maintains his innocence but all the evidence point back at him. Only Chae Gyeong believes that he is innocent and she is saddened by his troubles. Shin, knowing that someone actually cares and loves him, does not feel lonely anymore and is able to face the challenge with composure. Yul senses that it was all part of his mother's plan and he tells her to stop whatever she is doing, but her greed knows no bounds. As more incidents happen one after another, the existence of the Palace is being questioned by the people. In order to quieten the media, the King suggests that the Crown Princess be sent away. Chae Gyeong decides it was her role as Crown Princess to act in the best interest of the Royal Family and agrees. Chae Gyeong wants to show Shin the world that she once lived in and takes him out. They enjoy a day way from the Palace like a normal, everyday couple and make fond memories together.

In the midst of all this turmoil, Chae Gyeong and Shin's feelings for each other grow even stronger and they support each other to get through the storm. Chae Gyeong studies and tries hard to become someone who is a good match for Shin but the two are more alike than they realize. The King says that, "Apart from the truth of the incident, the person worthy of the imperial throne is the one who receives the love and honor of the people." Hwa Yeong smiles in satisfaction and throws in her last card. The Queen sees that Chae Gyeong has slowly started to show the qualities of a Crown Princess and for the first time, they actually sit down for a talk. The Queen showers her with encouragement and kind words. With the warm concerns of her mother-in-law and token of love from her husband, Chae Gyeong feels a strong responsibility to protect her new family and once again, rises with a firm determination...