2019–present: Solo and subunit activities
In 2019, Han appeared on episode 197 of King of Masked Singer, competing under the alias Imgeokjjeong. In October 2022, he appeared on episode 32 of LeeMujin Service where he performed a jazz-inspired remix of Stray Kids' then-new release "Case 143", as well as songs by Twice, YB, and Se So Neon.
Individually, Han has participated in special performances for Korean music festivals, including a cover of SSAK3's "Play That Summer" with Lia of Itzy and Juyeon of The Boyz at MBC Music Festival 2020, and a cover of Kim Sung-jae's "As I Told You" with bandmates Hyunjin and Felix at KBS Song Festival 2022.
As part of 3Racha, Han has performed with N.Flying at 2019 KCON LA, and on a remix of their pre-debut track "Runner's High" at 2019 KCON Thailand with Soyeon of (G)I-DLE and Hongjoong of Ateez. 3Racha have also given numerous performances, whether as an introduction, outro, or act independent of wider Stray Kids sets at the MAMA Awards, including a special stage at MAMA 2022 with Tiger JK and Jung Jae-il.
In February 2022, 3Racha announced their first official guest single "Just Breathe", a collaboration with Japanese rapper SKY-HI. In September 2022, 3Racha composed the track "Heyday" for the fourth soundtrack compilation of Street Man Fighter.
After a minor car accident which prevented the full Stray Kids lineup from originally performing as intended, Han made his first international festival appearance as part of 3Racha at the Global Citizen Festival 2023 in New York City.
In April 2020, Stray Kids sang the soundtrack for the anime adaptation of Tower of God, with 3Racha writing and composing for the opening theme "Top" and Han himself writing and composing for the ending theme "Slump". In October 2024, Stray Kids were invited back to create theme music for the second season of Tower of God, with Han co-writing and co-composing the opening theme, "Night". In July 2020, all members of 3Racha received writing and composition credits on Stray Kids' second domestic television OST, "Hello Stranger" for the drama Pop Out Boy!. In 2023, "Maniac" and "Venom" (written and produced by 3Racha, and from Stray Kids' sixth EP, Oddinary) were featured in the first season of XO, Kitty.
In April 2024, as part of 3Racha, Han co-produced Stray Kids' first OST for a Japanese drama, "Why?" for Fuji TV's RE: Revenge – At the End of Desire. In July 2024, 3Racha co-wrote and co-produced the Stray Kids song "Slash" for the Deadpool & Wolverine soundtrack, marking Han's first contribution to the soundtrack of a Hollywood cinematic release, and his second major film OST after 3Racha were approached to produce a theme song for Doraemon: Nobita's Sky Utopia. In September 2024, it was announced Stray Kids would perform "Come Play" with Tom Morello of Rage Against the Machine and Young Miko for the second season of Arcane.
In April 2025, it was announced Han had co-written a song for label-mates Nexz, "Run With Me", to be released on their second mini album, O-RLY?.
In March 2026, 3Racha wrote and produced the track "Endless Sun" for Bioré UV's "Sunlight is Your Spotlight" advertising campaign featuring Stray Kids. In April 2026, it was announced 3Racha would write and produce the debut title track "Hook" for MODYSSEY. The song debuted at 74 on the Circle Download Chart.
In May 2026, Han's first official individual guest feature was announced, the forthcoming track "Can't Love" with South Korean indie band Can't Be Blue.
After debuting, Stray Kids began a YouTube-based non-album singles project, SKZ-Record/Player, where individual members could upload solo and/or sub-unit original songs, cover versions, or dance performances, exploring their own artistic expression beyond the group's collective style. As of May 2026, Han was the most prolific contributor to the project, with thirteen original solo songs (in release order: "Close"; "I Got It"; "Alien"; "Wish You Back"; "Happy"; "Volcano"; "Miserable (You & Me)"; "13"; "Maybe"; "Human"; "Hold My Hand"; "Raining Stars"; and "Back to Life"), three original sub-unit songs ("Zone", as part of 3Racha; "Want So Bad", a duet with bandmate Lee Know; and "Respirator", a duet with bandmate Seungmin), one original duet with Bae of Nmixx ("1, 2, 3, 4, 5"), and two cover versions (both with bandmate Seungmin and both of songs by Day6). He was also credited as the lyricist and co-composer of "Hold On" and "Into the Current", recorded for the project by Seungmin, and "The Little Things", recorded for the project by I.N.
Six of these, plus a further, previously unheard solo song, "Run", were released to digital platforms as part of Stray Kids' digital compilation album, SKZ-Replay, in December 2022. As of July 2024, the remainder had yet to see wider release, though "Respirator" was performed in March 2024 on the final day of Stray Kids' fourth fan-meeting, SKZ Magic School. "Hold My Hand", first performed in August 2024 as part of Stray Kids' DominATE tour in Seoul, was later released as part of Stray Kids' special album, Hop, in December 2024, with an accompanying music video released to the band's SKZ-Record/Player YouTube project. In March 2025, as part of Stray Kids' digital single album Mixtape: Dominate, Han and Felix released a duet, "Truman"; an accompanying music video was released on the Stray Kids YouTube channel.
As of May 2026, Han has had several additional songs which had neither been released to SKZ-Record/Player nor to wider digital platforms, including "Scissor", which was performed at the Unite ON: Hallyu Festival in 2020, and "Don't Say", which was performed during Stray Kids' 5-Star Dome Tour in 2023, where Han played guitar during concert for the first time.
In October 2025, it was announced that together with bandmates Felix and I.N, Han would feature on the soundtrack for Netflix original series, Genie, Make a Wish, with the song "Genie". The song debuted at number 147 on the Circle Download Chart, and reached number 4 on the Billboard World Digital Sales chart. Later the same month, it was announced that Han would be releasing his first solo original soundtrack, "Updraft" (상승기류), for TvN's period drama Typhoon Family, on October 26, 2025. The song debuted at number 92 on the Circle Download Chart, number 68 on the Circle Background Music [BGM] Chart, and number 65 on the Circle V Coloring Chart.
In 2026, it was announced that Han's second solo original track, "Let It Show", would feature in the third season of drama series Yumi's Cells. Released on 21 April 2026, the song debuted at number 115 on the Circle Download Chart, number 121 on the Circle BGM Chart, and number 42 on the Circle V Coloring Chart. It peaked at number 110 on the Circle Download Chart a week later.