Weak Hero () is a South Korean television series written and directed by Yoo Soo-min with Kim Jin-seok and Park Dan-hee, starring Park Ji-hoon. It is based on the Naver webtoon Weak Hero by Seopass and Kim Jin-seok (Razen), which was published in 2018. The first three episodes premiered at the 27th Busan International Film Festival, which was held from October 5 to 14, 2022. The first season was released on Wavve on November 18, 2022. The second season was released on Netflix on April 25, 2025 as a Netflix Original.
Synopsis Class 1 Yeon Si-eun is among the top 1% of students in his class and is not interested in anything except studying. Though physically weak, he does not back down from the bullies in his classroom led by Jeon Yeong-bin. Using his quick decision-making skills, knowledge of multiple subjects, and the objects in his surroundings, Si-eun protects himself from their escalating acts of violence. But when he gets in grave danger, he receives help from Ahn Su-ho, the strongest fighter in their class, and Oh Beom-seok, the tormented son of an assemblyman. The three become friends as they try to survive a high school life full of violence and learn what it truly means to be strong.
Class 2 Si-eun has transferred to a new high school, Eunjang High School, and is still haunted by the trauma of his past failures. He builds new friendships with Park Hu-min, Seo Jun-tae, and Go Hyun-tak but must also face a more ruthless group known as the Union, an inter-school criminal gang led by Na Baek-jin and Geum Seong-je, which pushes him to confront even greater violence.
Cast Main Park Ji-hoon as Yeon Si-eun Jang Jae-ha as young Yeon Si-eun A model student in the top 1 of his class and a voluntary outsider who is only interested in his studies. He is physically weak so he protects himself with his quick analytical skills, knowledge of physics, and awareness of his surroundings. He has a pretty face but carries a lethargic expression. He is meticulous and usually quiet but is straightforward and curt in his speech, which can rub some the wrong way. When the lead bully in his classroom targets him out of jealousy, he does not back down and becomes entangled in a web of escalating violence. He gets unexpected help from Su-ho and Beom-seok, who become his allies and best friends. Choi Hyun-wook as Ahn Su-ho A free spirit who is the strongest fighter in his class. He does not care much for school and only comes in every day because of a promise he made to his grandmother that he would graduate with perfect attendance. Because he works as a delivery driver for his family's restaurant at night, he often sleeps in class. He was once training to become an MMA fighter. He is loyal and kind but has a quick temperament, often using his strength and fighting skills to solve disagreements. After Beom-seok convinces him to help Si-eun, the three boys become good friends. Hong Kyung as Oh Beom-seok A feeble and timid boy who wishes to become strong like the people around him. He was tormented relentlessly by bullies at his former school, forcing him to transfer. He is the adopted son of a wealthy assemblyman but experiences a tumultuous home life due to his father's physical and emotional abuse. His father claims to have adopted him simply as a publicity stunt. When he gets intimidated by Jeon Yeong-bin into helping him bully Si-eun, including sabotaging him in a test, he later wants to help Si-eun out of guilt and convinces Su-ho to come along. Though the three become friends and allies, Beom-seok's inferiority complex threatens to tear them apart. Ryeoun as Park Hu-min A student at Eunjang High School. Nicknamed Baku, Hu-min is known for his strength and sense of justice. He becomes one of Si-eun's main allies from Eunjang in the fight against school violence. Choi Min-young as Seo Jun-tae A student at Eunjang High School who was frequently bullied, but was inspired by Si-eun to fight back, and subsequently becomes one of Si-eun's ally from Eunjang. Lee Min-jae as Go Hyun-tak A student at Eunjang High School. Nicknamed Gotak, he is a loyal friend of Hu-min, and is known for his physical strength and courage. He supports Si-eun in several battles against school bullies. Yoo Su-bin as Choi Hyo-man The leader of Year 1 Class 3 at Eunjang High School, and the head of the delinquent students in the school. Bae Na-ra as Na Baek-jin A model student at Yeoil High School who is clever and possesses good fighting skills. He is the leader of the Union and is the main antagonist of Weak Hero Class 2. Lee Jun-young as Geum Seong-je A student at Kanghak High School. Seong-je is known for his brutality and loyalty to the Union. His presence intensifies the conflicts faced by Si-eun. He is seemingly Baek-jin's right-hand man.
Supporting Class 1 Lee Yeon as Yeong-i A courageous runaway who got involved with a dangerous gang of delinquents. She is bold and not shy around men, sometimes even joking about dating Si-eun. After her gang is dissolved, she stays with Su-ho for a while and starts working part-time at a restaurant. As she becomes closer friends with Si-eun and Su-ho, she becomes the target of Beom-seok's spiraling emotions. Shin Seung-ho as Jeon Seok-dae The leader of a group of delinquents, who gets involved with Si-eun and his friends when his cousin Yeong-bin asks for his help with taking revenge on Si-eun. He appears indifferent but actually cares deeply for his friends, especially Yeong-i and the youngest member of the gang, Sung-chan. Kim Su-gyeom as Jeon Yeong-bin A sadistic bully who targets Si-eun after he comes in second after him in a math competition. When Si-eun seems unfazed by his continuous threats, he resorts to increasingly more reckless and dangerous methods of bullying. After losing his first fight against Si-eun, he involves his cousin Seok-dae, a gang member, in their dispute and triggers a domino effect of escalating violence. Cha Woo-min as Kang Woo-young A young MMA fighter who holds a grudge against Su-ho after losing a match against him in middle school. Na Cheol as Kim Gil-soo The ruthless head of a group of delinquent runaways that coerces money out of teenagers through a rigged gambling app. Gong Hyun-joo as Si-eun's mother A math lecturer that rarely spends time with her son due to her busy schedule. Si-eun often falls asleep to her online lectures. Kim Sung-kyun as Gyu-jin Si-eun's father and a national judo coach. Like Si-eun's mother, he barely spends time with his son due to his work and constant business trips and is unaware of what his son is doing. Jo Han-chul as Oh Jin-won, Beom-seok's adoptive father. A wealthy but cruel and prideful assemblyman. Yeon Jeong-hoon as Lee Jeong-chan, one of Yeong-bin's henchmen Hwang Seong-bin as Han Tae-hoon, one of Yeong-bin's henchmen Yeom Ji-young as their homeroom teacher Shin Jun-chul as a Korean literature teacher Kim Hyun as the principal of Byeoksan High School Oh Dong-min as Assistant Park, Oh Jin-won's aide Jo Young-geun as Oh Jin-won's secretary Lee Jae-hak as a gang member Jeon Kang-ho as a gang member
Class 2 Oh Gi-gwang as Do Seong-mok A member of the Union. Lee Myeong-ro as Baek Dong-ha A member of the Union. Son Bo-seung as Seoknam Gorilla A member who Baek-jin personally identifies as a potential member of the Union.
Special appearances Class 1 Cha Sung-je as Sung-chan A boy Jeon Seok-dae sees as his little brother. Jo Ah-young as Jeon Yeong-bin's friend (ep. 1) Jang Dae-woong as Kim Won-seok (eps. 2–3) Kang Jun-young as a police officer (ep. 3) Kim Tae-joon as a police officer (ep. 4) Kim Hyun as school principal (ep. 8) Byun Jung-hee as Ahn Su-ho's grandmother (ep. 8)
Class 2 Jo Jung-suk as Choi Chang-hee A reputable gangster who handles a bowling alley, and thefts and sales of motorcycles. He is Baek-jin's boss who enlists his help in laundering the money earned. Jeon Bae-soo as Park Jin-chul Hu-min's father who owns a fried chicken restaurant.
Episodes
Class 1
Class 2
Production Development It was announced by Jaedam Media in May 2021 that they had reached an agreement with Playlist to co-produce a drama adaptation of the popular Naver webtoon Weak Hero. It was later confirmed that Shortcake, the studio co-founded by director and screenwriter Han Jun-hee (Netflix's D.P.), would also be producing the drama. Yu Su-min, who had recently won Best Film at the Mise-en-scène Short Film Festival, would direct and write the series while Han would serve as creative director. For the action choreography and stunts, martial arts director Heo Myeong-haeng (Vincenzo) would direct and Ahn Ji-Hye (Squid Game) would serve as art director. The original soundtrack would be produced by Primary.
To create the gloomy and cold atmosphere the titular character is known for, Park Ji-hoon took inspiration from Won Bin's performance in The Man from Nowhere (2010) as well as Kwon Sang-woo in Once Upon a Time in High School (2004). The climax at the end of eighth episode is a direct homage to the final scene in the latter. Park also lost over 10 pounds of muscle to achieve Si-eun's weak appearance. The cast attended action school together for several months so they could safely film the intense action sequences.
Casting Class 1 In an interview to the press on November 30, 2022, director Han Jun-hee went into depth about the casting process for Weak Hero: Class One. Han had previously stated that they wanted to "invite actors who have great energy and could lead the next generation of Korean dramas and film." He said Park Ji-hoon, Choi Hyun-wook, Hong Kyung, Shin Seung-ho, and Lee Yeon were all new actors and that he believed Weak Hero to be an opportunity to introduce them to a wider audience and foster their careers. On the casting of Park Ji-hoon as the lead, Han revealed that the idol actor was originally suggested by Shotcake CEO and co-founder Lee Myung-jin. Lee was amazed with Park's performance in At a Distance, Spring Is Green (2021) and Han found it amazing as well when he viewed it. After reviewing more of Park's work and interviews, Han was convinced he could show various faces and wanted to see if one could be that of a universal student in his late teens. He believed director Yu felt something similar when the suggestion was brought to him. Han went on to further praise Park as "the only actor in his 20's that could create such an atmosphere" and commended his great attitude and consideration for the staff on set. On Choi Hyun-wook's casting, Han said that he first saw him in Taxi Driver (2021) and was curious about him, but it was his appearance in Racket Boys (2021) that made him call right away as he believed that Choi would become a difficult actor to get a hold of. Overall, Han stated, it was intuition and he found it fortunate that this cast was able to take the drama.
Class 2 Park Ji-Hoon reprise his titular role for the second season alongside Ryeoun, Choi Min-Young, Yoo Su-bin, Bae Na-ra, Lee Min-Jae and Lee Jun-young.
Promotion On September 22, 2022, the official trailer video of Weak Hero Class 1 was released on the official website of the Busan International Film Festival, YouTube channel, and Wave YouTube channel, while the second trailer and poster were released on November 7. As the official sponsor for 27th Busan International Film Festival, Wavve installed several brand booth including a photo zone for Weak Hero Class 1 at the Haeundae Beach. On the premier day of 27th BIFF, director Yoo Soo-min, creative director Han Jun-hee, and actors Park Ji-hoon, Choi Hyun-wook, Hong Kyung, Shin Seung-ho and Lee Yeon attended the festival's open talk event held at the Busan Cinema Center in Haeundae District.
The press conference and production presentation for the drama was held on November 16, 2022, at CGV Yongsan I-Park Mall in Seoul.