Main •
Lee Jong-suk as Jung Jae-chan 정재찬 •
Nam Da-reum as young Jung Jae-chan :A 29-year-old rookie
prosecutor. Jae-chan was the son of Jung Il-seung, a police chief officer who was murdered by the same runaway soldier who killed Hong-joo's father. Back in his adolescent years, he was a carefree boy with no worries about his studies. After reconciling with his father, he became a changed teenager and aimed to work as a prosecutor. It was also at this age that he acquired from Hong-joo the ability to see the future through dreams, when Hong-joo saved him from drowning in a lake while preventing police officer Choi Dam-dong, the runaway soldier's older brother, from committing suicide. :Despite appearing cold and lacking a sense of humor, Jae-chan is still foolish and funny in some aspects. Since the first appearance of his future-seeing dreams, he will do everything he can to prevent them from coming true. He falls in love with Hong-joo after days of going out with each other, without knowing or recognising that she was "Bamtori" , his childhood acquaintance who also lost her father to the runaway soldier (his lack of recognition was due to him remembering Hong-joo as a boy from her tomboyish mannerisms and short, boy-like haircut). He was born in April 1988, and his blood type is B. Despite all the chaos he somehow managed to fall for Nam Hong-joo and is very protective towards her. •
Bae Suzy as Nam Hong-joo 남홍주 (a.k.a. Bamtori) • as young Nam Hong-joo : Born in 1988, Hong-joo is a 29-year-old
journalist and
field reporter who has the power of
precognition (the ability to see events in the future), which takes effect while dreaming. She was once a tomboyish girl nicknamed "Bamtori" () who aspires to become a baseball player. Since she was a child, Hong-joo has been haunted by seeing the deaths of other people in her dreams, one of which is the untimely death of her father, Nam Chul-doo, at the hands of a runaway soldier who also killed Jae-chan's father. She first met Jae-chan when both their fathers' funerals were jointly conducted on the same date in the same funeral hall. By saving Jae-chan from drowning, she had inadvertently made Jae-chan acquire the same ability that she has. Due to her short haircut and tomboyish characteristics, many people, including the reporters of the runaway soldier case and Jae-chan mistook her as a boy. : Now that she is fatherless, Hong-joo began dreaming of the impending deaths of her mother, Yoon Moon-sun, and herself: the former happening due to an accident she gets into and the latter due to her occupation as a field reporter. Unfortunately, like all the other dreams, she does not know when the deaths will happen; she can only guess. In her attempt to stop her dreams from becoming reality, she leaves her job and helps her mother in running a
samgyeopsal restaurant. Nevertheless, she regains her resolve in doing her job as a field reporter with Jae-chan to support her in preventing their dreams from coming true. She later in the series falls in love with Jae-chan and begins dating him. •
Lee Sang-yeob as Lee Yoo-beom 이유범 •
Yeo Hoe-hyun as young Lee Yoo-beom :A 34-year-old successful and famous prosecutor turned
lawyer who does not hold any attachments. Yoo-beom was Jae-chan's private tutor when Jae-chan was in his adolescence. He coaxed Jae-chan into falsifying his report cards so that they could gain money from Jae-chan's father and buy a motorcycle. With Yoo-beom driving the new motorcycle, they get into an accident and he leaves Jae-chan behind to fend for himself, an incident which made Jae-chan dislike him. :As a former prosecutor, Yoo-beom dared to falsify evidence just to finish his cases. As a lawyer, he works in Haekwang Law Firm, taking on any case that brings him a lot of money and going to whatever lengths to achieve an outcome he desires, such as fabricating evidence or manipulating testimonies even if he knows if his clients are truly guilty or innocent. He even went as far as to murder Ha Joo-an, the true culprit of the IV drip serial murders to cover up the fact that he fabricated evidence that wrongly convicted a doctor for perpertuating the 19 killings. Yoo-beom was eventually found guilty of murder and fabrication of evidence and sentenced to
incarceration for life. :He was Hong-joo's boyfriend because of a blind date. However, they broke up after Jae-chan saved her from the accident that night. Yoo-beom's birthday was November 20, 1983. •
Jung Hae-in as Han Woo-tak 한우탁 :A 29-year-old
police officer who was the top placer in his class of aspiring policemen. Woo-tak is considered to be a handsome, intelligent, and able-bodied police officer. Although he exemplifies the ideal policeman, he keeps a secret that can jeopardize his career in the police: he is actually suffering from
color blindness but an error in the assessment made his condition undetected. :Woo-tak was destined, without him knowing, to die in a car accident that Yoo-beom will cause on a snowy Valentine's Day after he delivered Yoon Moon-sun's cellphone which she left at her restaurant. Thanks to Jae-chan, who intercepted Hong-joo's car which Yoo-beom was driving, he was saved from his supposed death and acquired from him the ability to see future events through dreams. Together with Jae-chan and Hong-joo, they work together to keep their bad dreams from coming true. As the trio went on with their lives, Woo-tak began having an affection for Hong-joo, although he kept his feelings concealed, sensing that Hong-joo and Jae-chan are developing feelings for each other. His birthday was in September 1988, and his blood type is O.
Supporting Division 3 •
Ko Sung-hee as Shin Hee-min 신희민 :A female prosecutor with a charming and friendly appearance. Prosecutor Shin was Jae-chan's colleague when they were in college, but she holds a higher position than Jae-chan in the prosecution office, next to their superiors. She also has a high success rate at prosecuting criminals, though she sometimes finds it hard to accept her own mistakes, especially her failure in Kang Dae-hee's poisoning case. • as Lee Ji-kwang :A senior prosecutor who became close to and supportive of Jae-chan. He is willing to cover up for Jae-chan and to let him borrow his personal things, even his own car. He began to secretly date fellow prosecutor Son Woo-joo. Later on, their secret affair was accidentally revealed to their co-workers when he wore by mistake Prosecutor Son's lipstick which he inadvertently switched with his lip balm. •
Bae Hae-sun as Son Woo-joo :Another senior prosecutor who was a single mother unbeknown to her co-workers. She became close to Prosecutor Lee and ended up being married to him. •
Lee Ki-young as Park Dae-young :Chief of the Prosecution Officer Division 3 who is very conscious about his division's reputation and performance. He has the same name as a mobile phone thief whom he indicted ten years ago when he was still a prosecutor. •
Kim Won-hae as Choi Dam-dong • as young Dam-dong :A police officer turned
detective/inspector who works for Jae-chan in the Prosecution Office. Choi Dam-dong was the older brother of Choi wook-hyun, the runaway soldier who killed Dam-dong's chief and Jae-chan father, Jung Il-seung, and Hong-joo's father, Nam Chul-doo. During his younger years as a police officer, he attempted to commit suicide by drowning himself in a lake out of the shame he felt for Wook-hyun's crimes. Before he completely drowns, Jae-chan and Hong-joo save him and convince him to move on with his life. From that moment on, he wished he could meet them once again in the future. :Now an old detective, Inspector Choi's skills as a former policeman are still in action, particularly when it comes to crime scenes. He once worked for ex-prosecutor Yoo-beom, though he was unaware of Yoo-beom's fraudulent schemes until when he began working for Jae-chan. He began supporting the unknowing Jae-chan in his investigations and gives him helpful advice. He also talks formally to Jae-chan even though he is much older than him. It is also revealed in the latter episodes of
While You Were Sleeping that he had also acquired the ability to see the future through dreams, apparently from Hong-joo and Jae-chan. •
Park Jin-joo as Moon Hyang-mi :Jae-chan's assisting officer who likes handsome men but can get easily turned off. • as Min Jung-ha •
Lee Bong-ryun as Go Pil-suk
People around Jung Jae-chan •
Shin Jae-ha as Jung Seung-won, Jae-chan's 19-year-old younger brother who was born in 1998. He is the boyfriend of a famous pianist named Park So-yoon • as young Jung Seung-won
People around Nam Hong-joo •
Hwang Young-hee as Yoon Moon-sun, Hong-joo's widowed mother and the late Nam Chul-doo's wife; a
samgyeopsal restaurant owner. She was supposed to die due to exhaustion to compensate Han Woo-tak's death (due to the fact that his death happened after he delivered her left-behind phone and she was also Hong-joo's only family) and Hong-joo's hospital bills. It is thanks to Jae-chan's intervention that averted this horrible fate and she became a caring motherly figure to Jae-chan, Woo-tak and Seung-won.
Others • as Oh Kyung-han :a police officer along with Han Woo-tak; he sensed that Woo-tak had color blindness but kept the secret to himself to prevent Woo-tak from getting discharged •
Oh Eui-shik as Bong Du-hyun (SBC reporter; Hong-joo's senior) • as Dong-kyun (SBC reporter) •
Pyo Ye-jin as Cha Yeo-jung (Police officer who has a crush on Han Woo-tak) •
Yoo In-soo as Seung-won's classmate
Special appearances •
Kim So-hyun as Park So-yoon (Ep. 2–8, 16, 32) :a young pianist who suffers from her father Jun-mo's abusiveness; Seung-won's girlfriend •
Jang So-yeon as Do Geum-sook, So-yoon's mother (Ep. 3–8) :So-yoon's mother who is fearful and submissive to her abusive husband Jun-mo •
Um Hyo-sup as Park Jun-mo, So-yoon's father (Ep. 3–8) :So-yoon's abusive father; Lawyer Lee Yoo-beom's regular client •
Choi Won-young as Nam Chul-doo, Hong-joo's father (Ep. 3–4) :Hong-joo's deceased father; a bus driver who was killed by the runaway soldier who also killed Jung Il-seung •
Jang Hyun-sung as Jung Il-seung, Jae-chan's father (Ep. 1, 5–8) :Jae-chan's deceased father; the former police chief officer of Il-yoo Police Station before he was killed by the runaway soldier (his subordinate Choi Dam-dong's younger brother) who also killed Nam Chul-doo •
Hong Kyung as Choi Wook-hyun (Ep. 3, 6, 29, 31) :a soldier who deserted from the army and during the escape, he used a rifle to kill Jae-chan's father and detonated a grenade on a bus, causing both himself and Hong-joo's father to die in the explosion. It is later revealed that he was the younger brother of Choi Dam-dong. •
Lee Jung-eun as Jae-chan's mother (Ep. 5–6) • as Kang Cho-hee (Ep. 10–13, 15, 32) :Dae-hee's younger sister, an employee in a coffee shop. Her brother Dae-hee had killed her second brother Byung-hee for insurance. She was originally set to be murdered by Dae-hee for her insurance as well but survived the murderous rampage with Hong-joo and Woo-tak's help •
Kang Ki-young as Kang Dae-hee (Ep. 9–13) :Cho-hee's older brother; a chicken restaurant owner who killed his younger brother for his insurance; one of Lawyer Lee Yoo-beom's clients; initially acquitted of killing his brother, he was once again arrested and after a retrial, he receives a
life sentence for his brother's murder in the end •
Kang Shin-hyo as College student (Ep. 10) •
Shim Wan-joon as Bearded man •
Shin Eun-jung as Kim Joo-young, judge (Ep. 11–12) •
Lee Do-gyeom as Myung Dae-gu (Ep. 13, 24–32) :Seung-won's classmate and son of Myung Yi-suk, a doctor who was falsely accused as the culprit of an intravenous drip serial killing of 19 hospital patients. Even after his father was convicted and sentenced to life imprisonment and after his father's death by suicide, Dae-gu sought to help his father prove his innocence, and he harboured a strong sense of hatred towards Yoo-beom ever since •
Baek Sung-hyun as Do Hak-young (Ep. 13–17) :Woo-tak's high school roommate and internet installer who was falsely accused of being the culprit behind Yoo Soo-kyung's sudden death •
Cha Jung-won as Yoo Soo-kyung (Ep. 13–16) :a nationally renowned athlete in archery who is very much loved by the people around her because of her virtuousness and generosity. She died when an attack of fainting spells due to
otolithiasis caused her to collapse and injure her head, leading to severe cerebral hemorrhage. • as Yoo Man-ho (Ep. 15–18, 32) :a skilled marksman who is suffering from pancreatic cancer and is in terminal condition. He is Soo-kyung's father, becoming one of Lawyer Lee Yoo-beom's clients for her daughter's case. • as Chan-ho (Ep. 19–21, 32) :Prosecutor Son's son who suffers from chronic
kidney failure •
Lee Ga-ryeong as hospital administrator in charge of organ donation who tells Son Woo-joo about a kidney donor for her son (Ep. 21 19:15) • as Lee Hwan (Ep. 19–24) :Professor Moon Tae-min's teaching assistant and an organ donor to seven patients (including Chan-ho). He was one of the victims of Professor Moon's abusiveness, from which he got his injured arm. He was secretly killed by Professor Moon after he attempted to reveal Professor Moon's wrongdoings during a book launching activity. • as Hwan's father (Ep. 21–24, 32) • as Moon Tae-min (Ep. 21–24) :a seemingly benevolent professor and writer who is abusive to his students and subordinates in reality. He secretly killed Lee Hwan after a book launching ceremony. He is one of Lawyer Lee Yoo-beom's clients. •
Yoon Kyun-sang as couple in meadow (Ep. 21) •
Lee Sung-kyung as couple in meadow (Ep. 21) • as the Judge (Ep. 21–22) • as Park Dae-young, a mobile thief (Ep. 25–26) :a mailman turned thief whose nine-year-old daughter became paralyzed after a car accident. With her daughter needing constant care at home, he abandoned his job and resorted to stealing mobile phones. He has the same name as the prosecutor who sent him behind bars. Her daughter died ten years ago while he was in jail. :Dae-young continued his crime even after he was out of jail and stole Ha Joo-an's phone in the process. He copied Joo-an's files in a flash drive before giving it to Jae-chan for investigation. • as Jo Yoon-pyo (Ep. 25–26) :Ha Joo-an's accomplice who knew about Joo-an's crime. He was asked to retrieve the phone which contained the photos of Joo-an's 19 victims. He was then killed by Joo-an after he got caught by the police. •
Lee Eun-woo as Ha Joo-an (Ep. 28–29) :the real culprit of a seriously dreaded intravenous drip serial killing of 19 hospital patients. She was a bed-ridden patient suffering from
Crohn's disease. Out of her intense animosity towards her fellow patients who were already about to be discharged, she injected her first 11 victims with
Vecaron. She killed her remaining eight targets in the same manner after the arrest of the doctor Myung Yi-suk, who was first assumed to be the culprit of the crime. She also kept photos of her victims in her phone, which was stolen by the thief Park Dae-young and the contents revealed to Jae-chan and his team. During her appearances in the show, Joo-an had never shown any tinge of remorse for her actions. She was killed by Lawyer Lee Yoo-beom, who threw her off the building and let her fell to her death after she attempted to murder Hong-joo. •
Son Byong-ho as Lawyer Ko Sung-ho, Representative of Haekwang Law Firm (Ep. 29–31) ==Episodes==