one friend is Young-gyu. Baro as Ki Young-gyu A developmentally disabled teenage boy with the mental age of a six-year-old. He is Saet-byul's friend, and tries to save her from the kidnapper. Han Sun-hwa as Jenny She started out as a con artist who'd already been to jail five times, until Dong-chan hired her as a fraud detection expert. Supporting characters Park Hye-sook as Jang Mi-soon Soo-hyun's mother. Kim Jin-hee as Joo Min-ah Soo-hyun's junior colleague who had an affair with Ji-hoon. She became pregnant with his child, but miscarried when she fell down the stairs while Ji-hoon was forcing her to go to an abortion clinic. Jung Hye-sun as Lee Soon-nyeo Mother of Dong-chan and Dong-ho. She takes care of her grandson Young-gyu. Jung Eun-pyo as Ki Dong-ho Dong-chan's older brother, and Young-gyu's father. Falsely accused and imprisoned for the murder of Dong-chan's girlfriend, Soo-jung. Shin Goo as Choo Byeong-woo A businessman disguised as a homeless bum. Ahn Se-ha as Na Ho-gook Dong-chan's junior colleague when he was in the police force. Yeon Jae-wook as Wang Byeong-tae Expert hacker who works at Dong-chan's private investigator office. Kang Shin-il as Kim Nam-joon The President of South Korea. Joo Jin-mo as Lee Myeong-han Presidential chief of staff. Ye Soo-jung as Park Ji-young The First Lady. No Min-woo as Theo After witnessing his beloved older brother's suicide, he went into a long period of depression. He decides to fulfill his brother's lifelong dream of becoming a musician in his place, and successfully becomes the front man of the rock band Snake. He is Saet-byul's favorite idol singer. However, unforeseen events threaten to quash his dreams altogether when the shoe of a missing child is discovered in his van. Although he isn't prosecuted as a criminal, he is still considered as a possible suspect in the case. Oh Tae-kyung as Jang Moon-soo or Chang Moon-soo Owner of stationery shop. Im Ji-kyu as Ryu Jin-woo Park Min-jung as Mimi Jang In-sub as Manager Kim Min-chan as Soo-hyun's junior colleague (ep 1) Lee Yeon-kyung as owner of Destiny Cafe (ep 1) Kim Il-joong as MC (ep 1–2) Lee Seung-hyung as TV director/PD (ep 1–2) Joo Ho as Kim Joon-seo (ep 2) The President's son. Kang Sung-jin as Cha Bong-sub (ep 3–6) Serial killer who murdered three women, including Young-gyu's mother and Dong-ho's friend Mimi. Kwak Jung-wook as Han Ki-tae (ep 5–6) Kang Byul as Ki-tae's