2011–2016: Beginnings Ko debuted in 2011 in
Spring Awakening while attending college, and later performed in
Fame,
Grease and
Spamalot, among others. Finding himself unemployed after
Fame ended, he returned to his hometown in Daejeon and worked part-time as a courier for a while. His financial struggles prompted him to decide to temporarily quit musicals and move to the United States with the help of one of his middle school classmates who already lived there to find a different job, earn money, and try again with musical acting in the future. At the same time, Yang Joo-in, who directed him the previous year in
Goddess Is Watching, recommended he auditioned for the South Korean production of
Wicked because she thought his voice tone would fit it: originally, Ko had no intention of trying for the musical, lacking the desire to play a "cool character" and having a preference for non-mainstream roles, but Yang's words convinced him to change his mind. He took the audition without aiming for a specific character, since he liked the
Wicked numbers but had only heard of
Elphaba's and
Glinda's before, and was ultimately cast as
Fiyero. Even though he struggled to resonate with the character's reasons at first, the role brought him further recognition as a musical actor thanks to his stable acting and singing skills, and he abandoned the plan to emigrate.
2016–2020: Phantom Singer and military enlistment Ko's career took off after appearing in the first season of JTBC's audition program
Phantom Singer from late 2016 to early 2017, where he won third place as part of vocal quartet Hpresso. While on the show, he starred as mutant Romeo in
Romeo and Juliet, a new interpretation of
Shakespeare's
tragedy set in a world shaken by a nuclear war. At the end of 2017, he was double-cast with
Hong Kwang-ho as the titular character in
Hamlet: Alive. Having stayed close to fellow
Phantom Singer contestant and Hpresso member Kwon Seo-kyung for two years, in June 2018 Ko collaborated with him to release a duet extended play,
Musica, which included their eponymous cover of
Paolo Meneguzzi's song first seen on the show. To commemorate the release of the album, they held a joint concert at Lotte Concert Hall on September 2. Later that month, Ko applied for the army band to fulfill his mandatory
military service and enlisted the following November. While serving he starred in the army's original musicals
Shinheung Military Academy and
Return. He was discharged on June 23, 2020, and chose the musical
Murder Ballad, which would open in August, as his comeback work. At the same time, he was cast as
Anatole Kuragin in
Great Comet, the Korean version of
Natasha, Pierre & the Great Comet of 1812 by
Dave Malloy.
2021–present: First album, ''Tomorrow's National Singer'' and further roles In January 2021, Ko reunited with Hpresso and returned to
Phantom Singer after four years for a special "All Stars" edition which gathered the top 3 groups of all previous editions. He was then able to perform in
Great Comet, which premiered on March 21 after being postponed due to the
COVID-19 pandemic in South Korea. Celebrating his 10th debut anniversary, Ko released his first solo album, an EP titled
Start Over, on April 13, 2021. He also held his first solo concert at the Blue Square Mastercard Hall in Yongsan-gu, Seoul, on the 12th and 13th of June. Later in July, he performed as the titular character in
Hedwig: he was hesitant to accept the role at first, fearing that he might ruin the show if his performance was poor, but was praised by the audience for his powerful vocals, diction, and natural stage presence. While starring in
Hedwig, Ko joined TV Chosun's K-pop audition program ''Tomorrow's National Singer
and ranked 6th overall, embarking in a nationwide concert tour with the other members of the top 10 as part of group KKD. In April 2022, he was cast as Light Yagami in Death Note, a musical based on the best-selling manga of the same name. It was followed by a starring role as Tony in West Side Story, which ran from November 2022 to February 2023 in Seoul. Ko then released an EP in French, Les Chansons
, which included covers of Hymne à l'amour by Edith Piaf and Le Festin
from the original soundtrack of Ratatouille; he held a commemorative concert for it at Lotte Concert Hall on March 4, 2023.Ko received an offer to appear in Memphis, a musical based on the true story of DJ Dewey Phillips, at the same time he was performing in West Side Story''. Despite not being impressed by main character's Huey solo, "Memphis Lives in Me", that they played for him, he did some more research and found the other songs to be upbeat and good. Since the production was not a replica of the original musical, which deals with
racial discrimination in 1950s America, he felt that there was room to adapt it to Korean sensibilities and that he could make it entertaining, so he accepted the role. Ko began 2024 by reprising his role of Anatole in
Great Comet, which earned him the Best Supporting Actor award at the 9th Korea Musical Awards. and in
The Rose of Versailles, from the
same name manga series by
Riyoko Ikeda. In December, he was cast as the titular character in the musical
Cyrano, an adaptation of the play
Cyrano de Bergerac by
Edmond Rostand, based on the true story of
Savinien de Cyrano de Bergerac. In the meantime, he voiced Fiyero in the Korean dub of the American musical film
Wicked by
Jon M. Chu. He also returned to
Memphis as Huey after two years, and joined the musical
Man in Hanbok, which blended European stage aesthetics to Korean sentiments with a double setting in
Renaissance Italy and
Joseon Korea, in the dual role of genius scientist Yeong-sil and modern scholar Kang Bae. At the same time, he reprised his part as Fiyero in the Korean dubbing of
Wicked: For Good, while also providing the voice to the Cowardly Lion and Chistery. == Artistry ==