Hello Monster

Hello Monster (lit. I Remember You) is a South Korean television series starring Seo In-guk, Jang Na-ra, Choi Won-young, and Park Bo-gum. It aired on KBS2 from June 22 to August 11, 2015 every Monday and Tuesday at 21:55 for 16 episodes.

Despite the show's lacklustre ratings, audiences and critics alike praised its story and the performances of the cast, particularly Park Bo-gum's performance.

Synopsis
Genius profiler Lee Hyun (Seo In-guk), returns home to Korea after something from a case he has been sent triggers a memory he thought he had lost forever. Unbeknownst to him, one of his team members, Detective Cha Ji-an (Jang Na-ra), has been investigating him for some time. She is aware that his father was murdered and his brother disappeared under mysterious circumstances involving a criminal named Lee Joon Young (Doh Kyung-soo) -- whom they both want found and incarcerated. Each seeks to unravel the other, unaware that they've been drawn into a dangerous game of cat and mouse by a master player and that both truth and evil are closer and far more twisted than they think.

Main

 * Seo In-guk as Lee Hyun / David Lee
 * Hong Hyun-taek as young Lee Hyun
 * Lee Hyun was a "strange child" who caught the attention of his father, a police inspector, who later confined him in a small room to prevent him from breeding criminal thoughts. An intelligent child, he later studies abroad and becomes a reputed professor. Strangely, he loses his childhood memories, and a series of events lead him to return to South Korea. There he tries to solve numerous murder cases that seem to be linked to one another in order to find his long-lost little brother, whom he presumed to be the serial killer.


 * Jang Na-ra as Cha Ji-an
 * Park Ji-so as young Cha Ji-an
 * Cha Ji-an's father mysteriously disappeared together with Lee Joon-young, a convicted prisoner who was said to have escaped from confinement. She becomes a police inspector and meets Lee Hyun, the boy she has been stalking since her childhood. Their similar circumstances lead them together as they work to solve criminal cases.


 * Choi Won-young as Lee Joon-ho / Lee Joon-young
 * Doh Kyung-soo as teen Lee Joon-young
 * Born as a result of rape, Joon-young was neglected as a child. He soon bred murderous thoughts and became a murderer who eventually escaped from prison. 20 years later, he returned with the identity of Lee Joon-ho. His main personality trait throughout the series was depicted as someone who doesn't understand complexities of human emotions while being well versed in their thoughts. For-example, from his perspective, his returning of Cha Ji-an's father's remains was a good deed despite having killed and framed the guy himself. Knowing how her father ended up 20 years ago made her angry at him but he was sad to see Cha Ji-an being angry and couldn't figure out the reason despite it being very obvious to others.
 * He doesn't think he ever did anything bad since there was always a justifiable reason for himself.
 * In his own words, Lee Hyun was the kid he wanted to be while Lee Min was the kid who came to resemble him.


 * Park Bo-gum as Jung Sun-ho / Lee Min
 * Hong Eun-taek as young Lee Min
 * Lee Min shared a close relationship with Lee Hyun as a child and often confided his darkest secrets to him. He feels neglected later on as he was under the misconception that he had been abandoned by his brother after their father was murdered. He later appears nearly 20 years later using the name Jung Sun-ho.

Supporting

 * Lee Chun-hee as Kang Eun-hyuk
 * The leader of the special investigator team and the son of the police commissioner.


 * Min Sung-wook as Son Myung-woo
 * Special investigator member and senior of Cha Ji-an. He is cynical and is annoyed by Lee Hyun's attitude.


 * Kim Jae-young as Min Seung-joo
 * The youngest member of the team. He is a bright young man who is cheerful.


 * Son Seung-won as Choi Eun-bok
 * Special investigator team member. He is a slightly quiet person. Unbeknownst to the team, he is one of the kids that Lee Joon-young saved from his hellish childhood life.


 * Im Ji-eun as Hyun Ji-soo
 * Planning director of the investigation team and Lee Hyun's adoptive mother.


 * Nam Kyung-eup as Kang Seok-joo
 * Police commissioner and father of Kang Eun-hyuk


 * Lee Bom as Joon-ho's mother
 * She was raped and gave birth to Lee Joon-ho.

Guest and cameo appearances

 * Shin Dong-mi as Yang Eun-jung
 * Cha Ji-an's aunt.


 * Jun Kwang-ryul as Lee Joong-min
 * Lee Hyun's and Min's father.


 * Tae In-ho as Yang Seung-hoon
 * A chaebol, who is a serial killer and Jung Sun-ho's client


 * Choi Deok-moon as Na Bong-sung
 * Lee Hyun's indebted friend, who Hyun always ask a favor from


 * Lee So-yoon
 * Yoo Hyung-kwan as Yang Jin-seok
 * Park Gun-rak
 * Lee Won-jae
 * Ha In-hwan
 * Bae Ki-bum
 * Han Young-kwan
 * Yoon Dong-young
 * Dong Yoon-seok
 * Song Ui-joon
 * Shin Jae-ha as Park Dae-young (episode 5)
 * A serial killer whose motive is to avenge his mother and little sister's death


 * Kim Jong-gu as Shin Jang-ho
 * Jung Jong-ryul
 * Kim Kyu-chul as Park Young-chul (episode 5)
 * Park Dae-young's father, a prisoner who was accused of killing his wife and daughter


 * Seo Young-joo as Lee Jung-ha (episodes 6–7)
 * Lee Han-chul's son


 * Yoo Se-hyung as Lee Jin-woo
 * Lee Jung-ha's friend. His father was murdered by Lee Han-chul.


 * Ryu Sung-hyun as Lee Han-chul (episodes 6–7)
 * Lee Jung-ha's father, a serial killer and rapist


 * Lim Seong-eon as Ji Hyun-sook (episodes 9–10)
 * Myung-woo's blind date, who later was abducted by a serial killer and his girlfriend


 * Ko Kyu-pil as Park Soo-yong
 * Park Jae-woong as Do Jae-shik (episode 10)
 * A serial killer


 * Lee El as Kang Sung-eun (episodes 9–10)
 * Do Jae-shik's girlfriend and accomplice


 * Kim Min-kyung
 * Hwang Min-ho

Production
The first script reading took place in the end of April 2015 at the annex of KBS in Yeouido, Seoul, South Korea.

Ratings
In this table, the blue numbers represent the lowest ratings and the red numbers represent the highest ratings.


 * The drama aired with English subtitles on KBS World a week after its initial broadcast in Korea.