[8] Kim made his debut as a solo artist on June 19, 2018, with the release of his first EP D-Day, and its lead single "Sunset".

[12][13] Kim's second EP, titled D-Night, was released on October 17, 2018, with the lead single "Good Night Kiss".

[20] On June 25, 2020, Oui Entertainment announced that Kim will be one of the main casts for a TikTok X tvN D Story's web series, Trap, which will be aired starting on July 15, 2020.

[22][non-primary source needed][23] The group debuted on October 5, 2020, with their first EP, Identity: First Sight, with "Twilight" as the lead single.

[24] April 10, 2020, Kim underwent a tonsillectomy on after experiencing discomfort in his tonsils, even after several continuous medical treatment at the hospital.