11 years ago, Yoo Ae Yeon found out about the meetings between Dae Koo's mother and her husband. Filled with jealousy, Yoo goes to Dae Koo's home and hits his mother's head with a vase angrily. Dae Koo's mother is so badly hurt, she becomes unconscious. Terrified, Yoo calls her father and tells him that she has killed someone. After analysing Yoo Ae Yeon's personality, Dae Koo targets her weak areas and grills her at the interogation. Yoo breaks down. Being pushed to the corner, Yoo Ae Yeon becomes hysterical and swears to kill Dae Koo. (Source: Viu)