2003–2013: Serialized webtoons
Kang serialized Pure Love Comics on Daum from August 2003 to April 2004. The series averaged 2 million daily page views and reached a total of 60 million views by its conclusion. It was subsequently published as a two volume print manhwa and served as the basis for a 2008 film adaptation. The work demonstrated the viability of webtoons as One Source Multi-Use (OSMU) content. In November 2004, Kang signed a 10 million yen (approximately 100 million won) publishing deal with Japan's Futabasha, which marked a record for South Korean comic exports at the time.
In May 2004, he released the horror thriller Apartment, which follows an unemployed man living in a mysterious apartment complex. A film adaptation directed by Ahn Byeong-ki, titled Apt., was released in 2006. The film featured actress Ko So-young in her return to cinema and altered the protagonist's gender from the original webtoon. These early adaptations are credited with establishing the commercial viability of webtoons as source material for other media.
Between November 2004 and April 2005, Kang serialized the romance webtoon Babo, which centers on a mentally disabled man and his relationships with his sister and a childhood friend. The work was later adapted into a 2008 film starring Cha Tae-hyun and Ha Ji-won. In June 2005, Kang started writing supernatural fiction with the serialization of Timing. The story follows four individuals with unique temporal abilities (time stopping, rewinding, and precognition) who work together to prevent a series of deaths at a high school. Timing was Kang's first venture into the supernatural thriller genre and laid the groundwork for the "Kang Full universe." The series was released in print in August 2006 and adapted into an animated feature film of the same name in 2015.
In 2006, Kang's influence on the South Korean film industry with webtoon Pure Love Comics, Fool, Apartment, and Timing, were simultaneously in development for film adaptations. From April 10 to September 28, he serialized 26 Years, fictional thriller focusing on the offspring of individuals affected by the 1980 Gwangju Uprising who plot to assassinate former President Chun Doo-hwan. Kang considers 26 Years to be the most personally significant work of his career due to its historical and political themes. The webtoon was eventually adapted into a feature film 26 Years after years of production delays.
In 2007, Kang serialized the third installment of his romance series, I Love You (also known as Late Blossom), which focused on the relationship between an elderly milk delivery man and a woman who collects recyclables. The series was a commercial success on Daum, with monthly views growing from 2.7 million to over 6.3 million. It was later adapted into a 2011 film and a 2012 television series. Kang's success as a storyteller also led to his role as a screenwriter for major film productions. He was announced as the writer for the 3D sequel to Bong Joon-ho's 2006 film The Host in June 2007. Despite a high-profile announcement and a $12 million budget, the project faced production delays and was never realized in its original form. Kang then moved on to other serialized webtoon projects.
From June 9 to October 29, 2008, Kang serialized the mystery thriller The Neighbor. The plot centers on residents of an apartment building who begin to suspect a serial killer lives among them, exploring themes of social apathy. A 2012 film adaptation starring Kim Yoon-jin and Ma Dong-seok became a commercial success, drawing 2.4 million viewers. By the end of 2008, Kang's collected works had surpassed 300 million cumulative page views on the Daum platform.
In 2009, he released Again, the fourth installment in his "Mystery Psychological Anecdote" series. The story introduces a conflict between immortal beings and characters with temporal or telekinetic abilities. Again functions as a pivotal narrative link within the "Kang Full Universe," integrating the characters and supernatural elements established in his earlier work, Timing, into a broader shared continuity.
In August 2010, Kang began serializing Every Moment of Your Life (also known as Your Every Moment) on Daum's 'Manhwa-sok-sesang' platform. The series, which ran for six months, reached a total of 150 million views and averaged 2 million daily visitors. Departing from traditional romance, the story is set during a 2012 zombie outbreak in Seoul and follows a protagonist attempting to rescue his family from the city. The work was noted for blending the horror and romance genres, focusing on the emotional impact of the apocalypse.
From August 8 to December 6, 2011, Kang serialized the horror-mystery webtoon Lighting Store on Daum. The narrative focuses on a mysterious shop located at the end of a dark alleyway, which acts as a transition point for souls between life and death. Kang has acknowledged that Lighting Store is among his most complex works, noting that he intentionally moved away from his usual detailed exposition to allow for more reader interpretation. He suggested that while the plot contains various supernatural vignettes, the overarching emotional core is a woman’s reflection on love and loss. The series was highly successful and was later adapted into a 2024 Disney+ original series, which Kang also scripted.
On March 31, 2012, Kang marked his tenth year as a webtoon artist by hosting a book concert, Kang Full, 10 Years of Romance Comics, at Art Center K in Seoul. The event was the first of its kind for a South Korean webtoon author and featured guest appearances by fellow cartoonists Yoon Tae-ho and Joo Ho-min. During the event, Kang reflected on his career trajectory from his debut with Everyday Matters to his more complex supernatural thrillers like Lighting Store.
In 2013, Kang serialized his eleventh webtoon, The Witch from October 18, 2013 to June 20, 2014. The series centers on a man’s efforts to support a woman who has become a social pariah after being blamed for a series of misfortunes surrounding her. Moving away from the supernatural elements of his previous "Universe" works, The Witch returned to the mystery-romance genre. It was later adapted into a 2025 television drama on Channel A.
