S1 • E1
After their father's death, Sun Hee and Do Hee have been living completely different lives. Sun Hee is known to be a fool due to her way-too-kind nature. On the other hand, Do Hee becomes a top stewardess and lives a fancy lifestyle. One day, something unpleasant happens to Do Hee.
S1 • E2
While dropping by Do Hee's house to give her some side dishes, Sun Hee is attacked by a masked man. He tells her to bring something and that he'll give her four days. Sun Hee tells Do Hee about this, but Do Hee tells her that it's just one of her ex-boyfriends and to mind her own business.
S1 • E3
Do Hee comes to Sun Hee's place and collapses. She asks Sun Hee for a favor, and Sun Hee decides to pretend to be her sister and goes to work. To make matters worse, she is forced to fly as well. During the flight, she saves the chairman of Donghae Airlines, Oh Pyung Pan, and even runs into the famous pilot, Song Woo Jin.
S1 • E4
The plane suddenly going through turbulence, and Sun Hee is terrified. However, she notices that the chairman is missing and looks for him. She finds him in the restroom after he hits his head and helps him get back to his seat. While helping him, she hits her head and faints. Woo Jin hears that she's unconscious and checks up on her. Upon waking up, they accidentally kiss, and Woo Jin is more than just flustered.
S1 • E5
Sun Hee moves into the share house in place of Do Hee. There, she meets Woo Jin once again. He tries to close down the share house, and the two start to clash. She is shocked after finding out that her twin sister, Do Hee, likes him.
S1 • E6
Ok Jeong, Sun Hee's mother-in-law, moves into Sun Hee's house and calls her whenever she is out for too long. When Sun Hee comes home, Ok Jeong demands that she discloses everything she did while she was outside. Meanwhile, Sun Hee is determined to find the culprit who attacked her sister and goes through the contact list of Do Hee's phone.
S1 • E7
After seeing how furious Woo Jin is at her, Sun Hee gives up on Do Hee and his relationship and focuses on catching the culprit who attacked Do Hee. She finally finds a lead that will help her take one step closer to the culprit. Meanwhile, Ok Jeong suspects Sun Hee of committing adultery.
S1 • E8
Ok Jeong and Chun Ji video call Sun Hee and see Woo Jin behind her. They immediately confirm their suspicions of her having an affair and tell Chun Dae about it. Meanwhile, on the flight back to Korea from Japan, Sun Hee encounters a sick, elderly woman who vomits. Without any hesitation, Sun Hee cleans the vomit and comforts her. Upon seeing this, Ye Bin considers this odd.
S1 • E9
Sun Hee is once again attacked by the masked man in front of the share house. At that time, Woo Jin sees them and saves her. They go to the police station, and Sun Hee thanks him. Woo Jin tells her that if she is so thankful, she should move out of his house.
S1 • E10
Ok Jeong, Chun Dae, Chun Ji, and Moon Sook follow the GPS tracker to find out where Sun Hee is. They arrive at Woo Jin's house, and their suspicion of her having an affair is confirmed. However, Sun Hee pretends to be Do Hee and counter-attacks them. She even threatens to call the police on them for breaking in.
S1 • E11
Woo Jin corners and questions Sun Hee about why she claimed that they were dating. Not knowing what else to do, Sun Hee tells him that it is because she likes him. Woo Jin, who has been getting strange feelings toward Sun Hee, is even more confused. Meanwhile, Sun Hee says that she cannot demand the flight attendant to hand in her resignation letter.
S1 • E12
Tae Ree bans Sun Hee from flying, and Sun Hee begs her to lift the suspension. Just when Tae Ree is about to slap her, Woo Jin interferes and grabs Tae Ree by the arm. He then tells her that they are in fact in a relationship.
S1 • E13
Tae Yang tells Woo Jin that he will no longer allow him to steal everything that is dear to him. He tells Woo Jin to step away from Sun Hee. Woo Jin acts nonchalantly, but he is bothered by this. Meanwhile, Moon Sook goes to the department store to get a refund for the present Chun Dae got her, only to find out that he may be seeing someone.
S1 • E14
Woo Jin confesses his feelings for Sun Hee and also recruits her to be a main cabin crew for One Air. Sun Hee is glad that she did not ruin the relationship between Woo Jin and Da Hee. However, Cho Rong tells her that the one he fell in love with is not Da Hee but Sun Hee herself. Meanwhile, Kang Min decides to hold hands with Ye Bin.
S1 • E15
Chun Dae's double cheating is disclosed to his entire family, Moon Sook, and Sun Hee. Sun Hee is gravely hurt and feel betrayed. Meanwhile, Woo Jin runs into Sun Hee who is sharpening a kitchen knife in the middle of the night. He misreads the situation and believes she is mad at him for not taking any actions after confessing his feelings for her.
S1 • E16
Ye Bin tells Woo Jin that Do Hee has alcohol-related dementia. Upon hearing this, Woo Jin is bewildered. Meanwhile, Chun Dae apologizes to Sun Hee for cheating on her with two other women. He swears never to cheat ever again. However, Sun Hee's heart is too broken, and she does not know what to do.
S1 • E17
Kang Min urges Pyung Pan to flee for the time being, and he agrees to do so. After sending him off, Kang Min reports his fleeing. Now, Donghae Airlines is in Tae Ree's hands, and she can do whatever she wants. Meanwhile, Ye Bin finds out that Do Hee does not have alcohol-related dementia.
S1 • E18
In order to cut the food production cost for One Air, Sun Hee and Woo Jin go to the fish market together. There, they buy fish, and Sun Hee fillets it. Woo Jin is surprised to see this side of her and also falls in love with her once again. Meanwhile, Min Ji demands that Chun Dae pays for the things he bought for his family with her card.
S1 • E19
Sun Hee catches Chun Dae attending Soo Hyun's husband's funeral as a "host". He explains that he's just doing this out of friendship and that there is nothing going on between Soo Hyun and him. However, Sun Hee is shocked that he would dare to meet Soo Hyun once again. Meanwhile, Tae Yang finds out that the woman he fell in love with is not Do Hee, but Sun Hee.
S1 • E20
Pyung Pan is brought to Woo Jin, and he is having severe stomach pains. Not knowing what to do, Woo Jin asks Sun Hee for help, and she does her best to help Pyung Pan. Meanwhile, on her way home from a flight, Ye Bin spots Woo Jin and Sun Hee helping Pyung Pan into a car and takes a photo.
S1 • E21
Sun Hee pretends to be Do Hee and barges into Min Soo Hyun's restaurant with Sun Hee's coworkers. She surprises Soo Hyun and Chun Dae with evidence of their adultery. Furthermore, she tells her coworkers that they can eat there as they please and that Soo Hyun will pay for the cost. Meanwhile, Pyung Pan asks Woo Jin to take care of the company for him.
S1 • E22
Chun Dae hands Sun Hee, whom he thinks is Do Hee, a divorce paper, saying he already signed it. He tells her that he chose his wife solely because she was nice, but that now, Do Hee has ruined her. Sun Hee is hurt to hear these words. Meanwhile, while preparing for the test flight, One Air crew hears the news about the test flight getting canceled and One Air being sold to Chanmi Food.
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Cha Sun-hee
Song Woo-jin
Oh Tae-yang
Oh Tae-ri
Bong Chun-dae
Oh Pyung-pan
Joo Ye-bin
Lee Moon-sook
Bong Cho-rong
Kim Gong-joo