The duo was considered to be one of the most popular idols in that time and sold out millions of albums in South Korea and Asia.

Problems like lack of songs from composers, less support from his respected agency, and also a change of taste within the fans caused his first album as a solo artist to fail.

Kim was made the leader of the first series of Shootdori, where kids who are interested in soccer form teams and compete.

The music video of the lead single, Saying I Love You, featured Yoon Eun-hye, who was previously involved in a love-line with him in X-Man.

Kim also returned to television, becoming a permanent member of reality-variety show Family Outing since episode 19, part of SBS's Good Sunday lineup.

Family Outing has become one of the top-rated shows in Korea, consistently achieving the highest ratings for the Sunday mid-afternoon time-slot, and has gained online popularity among Hallyu fans.

The music video of the latter single featured fellow Family Outing cast member Park Ye-jin.

Kim gained pan-Asia popularity from the show, becoming one of the most searched Korean stars in Singapore, and having his showcase there sold out with more than 1,700 fans in attendance.

The eponymous lead single, 다시 (Again), which features Yoo Jae-suk, topped online music charts upon its release.

[18] On August 23, 2016, he officially made his singing debut in China with his first single, "Hate That Happiness Came" (恨幸福来过), produced by JJ Lin and lyrics written by Vincent Fang.

On December 19, 2020, Kim made history by becoming the first male celebrity, and 2nd person ever to win a Daesang in both Music and Entertainment.

[19] On June 17, 2021, Kim launched a fitness-focused YouTube channel "Gym Jong Kook" with 100,000 subscribers in the first five minutes.

[22] On April 28, 2023, Kim won the Baeksang Arts Award (Best Male Entertainer) for his work on Running Man, My Little Old Boy, and Gym Jong Kook.

"[citation needed] In January 2015, he was a guest on the popular talk show, Healing Camp, where he shed light on many personal controversies, including his choice to work as a public service worker instead of an active-duty soldier during his mandatory military enlistment, which was partly due to the aforementioned back issues.