In "A Gentleman's Dignity", after Jang Dong Gun finds out about his lost son, he broke up with Kim Ha Neul.
Seo Yi Soo was in a lot of concern when she couldn't get in contact with Kim Do Jin. During that time, Park Min Sook contacted Hong Sera, Seo Yi Soo, and Im Me Ah Ri and told them that Kim Eun Hee's son came back and the father is one of the four guys, Kim Do Jin, Im Tae San, Choi Yoon, and Lee Jung Rok.
Im Me Ah Ri said, "Honestly, the son looks like Do Jin Oppa" and Seo Yi Soo said, "No he doesn't, if a guy is handsome, does that mean they looke like Do Jin?" But later she finds out the reason behind why she couldn't get in contact with Kim Do Jin and becomes nervous.
Later Kim Do Jin met up with Kim Eun Hee and finds out that Colin is his son and goes to Seo Yi Soo with the truth. He says, "I am sorry for all the things I am about to say to you. I will cancel saying that we'll live together. I am breaking the promise that I will make you happy. I also will break the promise that I won't break up with you before you break up with me. I am a bad guy so please forget about me."
Seo Yi Soo asked, "Is he really your son?" and he said "Yes. It wasn't that I didn't have the courage to love one person forever, it's because I don't deserve to love one person. I think I am getting punished for all the hurt I caused through this boy. Try your best to forget about me."
She replied to him saying, "And then? Should I meet a good guy?" and he said, "Yes I really do hope so." To this, Seo Yi Soo said, "I was just really happy out of nowhere. There was a twist to all of this" and started to cry.
