Krystal Jung Soojung (24 years old)

Having to pretend as the Kim's real daughter for the sake of her death friend, Yoona, when she was 19 years old, she finally found what she had always wanted in her life. A family. And that family  also gave her one true love, Kim Jongin / Kai. Of course being an imposter had its downside. Despite being love by Taeyeon, Kai and also Kim Jongkook, the head of the Kim's family and his wife, she wasn't really well received by the elder of the Kim. Grandma Kim despised her shady background and had never taken a liking on her. When the Kims found out about the truth, they still accepcted her as their family , they even bethroted Kai with her. But not Grandma Kim. Thinking that a low class  person like Krystal would tarnish the family's name, she planned to separate her and Kai. And Krystal, for the sake of Yonghwa and Seohyun, bowed down to threats from Grandma Kim, choosing to leave Kai. But what happened when she lost her memories and met Sehun, Kai's step brother?

Kim Jongin/Kai (25 years old)

He had loved Krystal way way too much to let her go. She was his life, his soul, his air. But for someone as stubborn as Krystal, he couldn't change her mind when she chose to bow down to his grandmother's threat in order to save Yonghwa, Krystal's long separated older brother. He had to be a saint just for her, sacrificing his own happiness, their happiness. She wanted him to marry Sulli and in which he did unwillingly. Nevertheless, there hadn't been a day he could forget about her since she left. He thought she would be gone forever, but then she came back. Out of the blue. And this time, she lost her memories and worst of all, she would be his future sister in law!

Choi Jinri/Sulli (24 years old)

She never did love him. She was forced to marry him because of his wealth and fortune. Her true love died because of her father's cruelty. She knew that Kai will never love her and she was dead on to make things right again when Krystal returned. If only, things weren't as complicated as she had expected them to be....

Oh Sehun (25 years old)

Being the only son from his mother's previous marriage, Taeyeon and Kai had never  made him an outcast. They treated him like he was their own family.And he would do anything for both of them. But would he have the heart to let go of the woman that he had came to love for Kai?

Other characters.

Kim Taeyeon. (27  years old) Kai's and Sehun's older sister. Jonghyun's wife.

Lee Jonghyun. (28 years old)Taeyeon's husband. Yonghwa's best friend.

Jung Yonghwa. (28 years old) Krystal's older brother. Seohyun's husband. Used to be the enemy of the Kim's family.

Seo Joohyun. (26 years old) Yonghwa's wife. The Kim's cousin.