Since 2013, he has expanded his range of activities as a solo artist, and in 2023, he formed his own agency iNKODE where he serves as the Chief Strategy Officer.

Kim has acted in TV dramas including Sunao ni Narenakute (2010), Protect the Boss (2011), Dr. Jin (2012), Triangle (2014), SPY (2015), Manhole (2017) and Bad Memory Eraser (2024); and in films such as Heaven's Postman (2009) and Jackal is Coming (2012).

[5] In reaction to the matter, Kim uploaded a journal entry on his official fan club website, and said that he was informed of the existence of separate biological parents by his mother two or three years ago, and it had been quite a shock to him.

Life in Seoul was financially difficult and he took various odd jobs to pay for rent, food, and training fees; and even appeared as an extra in movies.

[7] In an interview, he admitted he used to be tone-deaf in primary school and was frequently ridiculed for his dream of becoming a singer, but managed to overcome it through practicing alone.

He enrolled Hanam High School (하남고등학교) in 2005[9] and Kyung Hee Cyber University (경희사이버대학교), majoring in Digital Media Engineering.

After TVXQ went on hiatus in early 2010, he and two other fellow band members Yoochun and Junsu formed a new trio boy group, initially known as JUNSU/JEJUNG/YUCHUN in Japan.

In 2009 Kim, Junsu and Yoochun, started a lawsuit against their agency, SM Entertainment, and separated from TVXQ, soon founding their own band, JYJ.

[19] In September the band released a studio album called In Heaven, which sold 350,000 copies and ranked first on the Gaon charts.

[31][32] On January 26 and 27, Kim held two days of special concerts at the KINTEX Ilsan to celebrate the launch of the album, as well as his birthday.

[37] A repackaged version of the album, WWW: Remove Makeup was subsequently released in January 2014 and included the title track "Heaven", a pop ballad with label-mate Gummy.

[38] To promote his first album, Kim embarked on his first Asia tour which traveled to regional countries like Japan, Taiwan and China.

[56] His third Japanese album, Love Covers II was released on July 29, 2020, and debuted at number one on the Oricon weekly chart.

[57] It was announced on August 30, 2020, that he would be singing the opening theme song for Noblesse, entitled "BREAKING DAWN" which was written and produced by Hyde.

[59] On September 18, 2020, Kim released "Even If I Call You" for the Mr. Heart (2020) web drama, marking his first Korean soundtrack performance in six years.

[65] On October 30, C-JeS Entertainment It was announced that Kim has urgently decided to cancel the Japan concert due to the aftermath of the Itaewon Halloween crowd crush.

[71][72] The group debuted on October 16, 2024 with their eponymous extended play, in which Kim solely wrote one of the album's tracks "Goldilocks Water".

[73][74][75] On September 6, 2024 at 12 AM KST, the two remaining JYJ members, Kim Jae-joong and Xia Jun-su, unveiled a teaser for their continued collaborative venture, JX[76][unreliable source?

The teaser features a voice-over narration by the duo, emphasising their longstanding support for each other amidst the challenges and hinting at a new chapter in their journey.

[80][81] In November 2009, Kim co-starred with Han Hyo-joo in the joint Korean-Japanese telecinema Heaven's Postman as a young man who delivers letters written by the living to the dead and helps lingering ghosts settle their earthly affairs.

[83] In August 2011, he starred in his first South Korean television series, Protect the Boss with Choi Kang-hee and Ji Sung.

[91] In January 2015, Kim starred in KBS2's thriller SPY as a genius analyst working for South Korea's National Intelligence Service.

[93][94] In 2017, Kim was cast in KBS2's time-slip drama Manhole, as a man who travels back and forth through time to stop a wedding from taking place.

[95] For the first time in 10 years, Kim returned to entertainment shows in South Korea with his appearance as a panelist for season 2 of Taste of Love in 2019.

[101][102] In 2022, Kim was cast as the lead male role in the Korean television drama Bad Memory Eraser co-starring Jin Se-yeon.

[103] He guest starred in the third episode of the television adaptation of the manga Waru - Who said it's not cool to work?, for which he also sang the theme song.

[107] He owned the largest number of shares in the company and served as the art director until it "closed for restructuring" due to COVID-19 issues in March 2020.

He was under the 55th Infantry Division in Cheoin District, Yongin to serve as an active-duty soldier for 21 months and was also a member of the military band.

[114] On April 1, 2020 during the COVID-19 pandemic in South Korea, Kim posted on his Instagram account claiming that he has tested positive for COVID-19 due to him "[living] carelessly, disregarding all of the cautions provided by the government.

[116] He further explained his reasoning for the initial post was to raise awareness of the dangers of the virus, noting he personally knows individuals who have been infected and his father recently underwent lung cancer surgery.