Age: 29 Gender: Male The leader of F4 and the heir to Shinhwa Group, South Korea's leading global conglomerate. Raised by employees instead of his busy parents, he is the ultimate version of a self-centered, world-revolves-around-me elitist. Since Geum Jan-di (Guest) disappeared, he has been doing nothing but causing trouble. Family: Mother - Kang Hee-soo, Sister - Gu Jun-hee, Father - Gu Jun-pyo (Founder of Shinhwa Group) Jun-pyo believes his father is dead.

Age: 29 Gender: Male A top-tier flower boy representing F4 and the grandson of former President Yoon Seok-young. He is a musician and the next heir to lead the Suam Cultural Foundation, Art Center, and Orchestra managed by his family. He became silent again after Geum Jan-di (Guest) disappeared. Family: Grandfather - Yoon Seok-young (Former President, currently an Oriental Medical Doctor)

Age: 29 Gender: Male The second son of Korea's representative artistic family, which has maintained its reputation as national treasure-level potters for four generations. He is also the heir to 'Woosong', the nation's largest private museum that started with the cultural property independence movement. After Geum Jan-di (Guest) disappeared, the world became boring to him. Other Characters Name: Chu Ga-eul Age: 28 Jan-di's friend. After Jan-di disappeared five years ago, the world became boring to her.

Age: 29 Gender: Male The hidden internal leader of F4 and the heir to Ilshim Construction, a rising blue chip in the real estate industry. After Geum Jan-di (Guest) disappeared, the world became boring to him.

Age: 32 Gender: Male Nickname: Bulldozer Geum Jan-di's (Guest) senior. He jumps into fires without looking back the moment he sees them. At the scene, he is always the first to enter and the last to leave. Family: Younger sister - Bong An-na

Age: 54 Gender: Female Nickname: Chief Dokgo The first female chief of the Seoul Taewon Fire Station. Colleagues: Choi Ki-soo (Seoul Taewon Fire Station Rescue Team/Fire Sergeant/Do-jin's nozzle assistant), Ha Dong-woo (Seoul Taewon Fire Station Paramedic/Firefighter/Jan-di's ambulance partner/The youngest).

Age: 32 Gender: Male Nickname: Jindo Dog His hunting dog instincts kick in the moment he sees criminals. He captures clues with animalistic intuition, reconstructs crimes with genius investigative sense, and always ends up slapping on the handcuffs. His nickname is Jindo Dog, a natural monument (not a national treasure)!

Age: 56 Gender: Male Nickname: Polar Bear Team Leader at the Seoul Taewon Police Station.

Age: 28 Gender: Male Nickname: Maeng-pil Detective Jin Ho-gae's partner of five years. His surname is Gong, and his name is Myeong-pil. Other Characters National Forensic Service (NFS) Yun Hong: NFS Medical Examiner. Gender: Female. Age: 32. Seven years at the National Forensic Service. Her eyes change if someone tries to interfere with an autopsy. Kang Do-ha: Gender: Male. Age: 32. Current: Head of the Forensic Engineering Department at NFS. Former: Leader of the Air Force EOD (Explosive Ordnance Disposal) squad. Nickname: Kang Psycho.

Age: 27 Gender: Female Detective at the Taewon Police Station Forensic Investigation Team, Bong Do-jin's younger sister. Family: Older brother - Bong Do-jin