She was someone that he never went for. If she walked past him on the street prior to this meeting, he would not have looked twice. He wasn't sure what made him so intrigued by her. Was it the way she cared for him? Was it the way she accepted his past and present self? In the crowd he was always with, he choose to be with her. 

Daisy Kim is a girl from a poor family but has an unrivaled sense of optimism. It all comes to a head when she is forced to transfer schools from Texas to Seoul. There she meets the infamous group of nine astonishingly good looking and rich boys who are known as NCT 127. The group's leader is Lee Taeyong, who is a spoiled heir to a world-leading conglomerate. He is joined by mysterious and breathlessly handsome Jeong Jaehyun. Taeyong enjoys the thrill of making Daisy's life miserable. Gradual

Summary: You were a normal girl just trying to live your life, until one night you were taken. Now you must deal with new information in your life,  while also coming to terms with the fact that your brother is not who you thought he was. 

She once cheated on him. What makes it worse she had a fling with a psycho. Now that psycho is coming back to ruin her marriage.