JEJU ISLAND, South Korea 2011.

A girl stands by the beach. Oh Hayoung, the name written on the name tag of her school uniform. Hayoung's hair hung freely in the beach breeze. The girl is in a dilemma. Hayoung came from Seoul, spent all of her savings, to meet with Mrs. Soo Ae. The woman who she hopes to be her biological mother.

Hayoung has lived in an orphanage, since she's 3. At that time, his father died because of cancer, Hayoung was rescued by the hospital and was kept in an orphanage until now, she was 16 years old. During that time, she searched the informations of her other family. Until one day Hayoung found a picture of her father and Mrs. SooAe in the hospital with two babies, Hayoung was sure, the photo was taken when she was born with her twins. After searching several times, Hayoung found the man she believed was her twin through a social media account. The man named Oh Sehun. Her twin brother who has a better life than Hayoung, because Mrs. Oh has indeed been married to a wealthy chaebol several times. The world is very unfair, Hayoung thought.

"Hey, who are you?"

Hayoung turned around, shocked. Now in front of her there was a man standing with his arms crossed. Oh Sehun, her twins. Hayoung thought.

"Hellooo? Who are you? I don't think you are invited to my party." The man named Oh Sehun scanning Hayoung from head to toe. At his 16th birthday party, Sehun was sure not have a costume party wearing school clothes, and besides the girl's school clothes were different from Sehun's school uniform.

Hayoung's chest was beating fast, before finally saying softly. "I want to meet your mother."

"Huh?" Sehun looked confused.

"I want to meet your mother, Mrs. Soo Ae. She is my mother." This time Hayoung said firmly. The girl had made up her mind to meet her biological family.

"HUH ?!" This time Sehun's confusion grew. Then he pulled Hayoung's arm, avoiding the crowd that afternoon, because soon his birthday party would begin.

Sehun pulled Hayoung into the hotel hallway. His chest was beating when he heard Hayoung's words. Twin sisters?! How is that possible, he thought. He knew his mother had been married several times and it was not impossible if suddenly he had an additional step brother or sister, but having a twin sister was unimaginable for Sehun.

"I know you must be surprised by my statements, but I have evidence. Let me meet Mrs. Soo Ae. first. I am so desperate now."

Sehun frozen, "let me look your evidence first. My mom isn't going to meet any people freely."

Hayoung looked at the thin man in front of her. Then she hesitantly gave him several sheets of file from her backpack. 

"There are some of my data files, there is my student report, information from the orphanage, health certificate, birth certificate and others." Hayoung said.

Sehun accepted the file while continuing to pay attention to Hayoung. The girl is still wearing a short skirt school uniform, and a backpack.

"Oh Sehun, you and I are twins who were born on the same day from the same mother. You are tall, im pretty tall for a girl. you have really long fingers, mine too! " Hayoung said nervously, this time while biting her finger nails.

Sehun watched Hayoung's file, naturally biting his fingernail, indicating that he was nervous. The two then meet glance. "Wait, do you have a habit of biting your nails? me too. it's so strange! right?!" Hayoung said enthusiastically.

"It's not strange at all. Isn't this a common habit!?” Sehun denied.

"Today is your birthday right? It's my birthday too! and hey! we even share