Lee Giuk (, born January 24, 2000), known mononymously as Giuk and formerly known by the stage name CyA (), is a South Korean musician, rapper, songwriter, and producer. He is the bassist and rapper of the South Korean alternative rock band Onewe (formerly known as M.A.S 0094 or MAS). He made his solo debut on April 20, 2023, releasing his first extended play (EP) Psycho Xybernetics : Turn Over with the lead single "Time Machine (2100)". His second solo EP Rise Waves was released seven months later on November 15, 2023, with the lead single "Scratch".
Career 2015-2016: M.A.S 0094 formation and debut In 2015, Giuk formed the band M.A.S 0094 with his four bandmates and they originally performed cover songs. He got his first writing credit through KOMCA on the band's first original single, "Butterfly, Finding Flower", released on August 13. He would continue to participate in the band's songwriting, and also started composing songs, with the singles "Feeling Good" and "Starlight." He made his official debut with M.A.S 0094 on The Show on August 2, 2016 with the band's performance of their song "After 15 Seconds".
On December 12, Giuk featured in the soundtrack "Promise" by Donghyun of Boyfriend for The Miracle OST Part.2.
2017-2018: MAS, The Unit and rebrand as Onewe On June 1, 2017, he signed with RBW Entertainment as part of M.A.S 0094, and the band's name was shortened to MAS. In October, Giuk participated in the survival show The Unit, auditioning with the other members of MAS, but they competed individually. He was eliminated in the 7th episode, placing 59th.
As a member of MAS, Giuk used the stage name CyA, and he continued to use this name when MAS re-branded and re-debuted under the name "Onewe" in June 2018.
2019-present: Re-debut with Onewe and other producing activities Giuk produced and featured in "Crazy & Crazy (Prod. CyA)" for labelmate Oneus' debut EP Light Us which was released on January 9, 2019.
Giuk officially made his re-debut with Onewe on May 13, with the release of their digital single album titled 1/4. Giuk took lead on writing and composing the song "Ring on my Ears" for the album, for which a music video was released on May 15. He then made his debut in Japan as a member of Onewe with their first Japanese single album Reminisce About All on June 7.
While continuing to participate in Onewe, Giuk also continued to write music for other groups. In 2020, he co-wrote, composed and arranged "Dizzy" for Oneus' fourth EP Lived which was released on August 19. In 2021, Giuk he co-wrote the lead single "Zombie" for Purple Kiss' second EP Hide & Seek and featured in the music video. He also acted in a main role alongside Purple Kiss member Goeun in the group's story films for the promotion of their following EP.
2023: Solo debut with Psycho Xybernetics : Turn Over, Rise Waves On March 9, 2023, RBW Entertainment announced that Giuk will no longer use the stage name CyA, and now uses his legal name, Giuk, for all official activities, including as a member of Onewe and his solo activities as an artist and producer.
On April 8 and 9, Giuk held his first solo concert Prologue: Turn Over in anticipation of his solo debut. Giuk officially made his solo debut on April 20, releasing his first EP Psycho Xybernetics: Turn Over with the lead single "Time Machine (2100)". On June 6, he held an encore concert Epilogue: Turn Over.
He wrote the lyrics and composed for the single "Save Me" for Mamamoo+ which was released on July 18 and included in the duo's first EP Two Rabbits released in August. He also co-wrote another song for labelmates Purple Kiss, titled "Mistake", and released in September as part of the group's first single album Festa. Giuk is the featured artist for the title track "A Girl's Panorama" from YongYong's first full-length album MyMy which was released on November 9.
On November 11, he held a solo concert entitled "Flight1112". Giuk released his second solo EP Rise Waves on November 15, with the lead single "Scratch".
2024-present: Onewe's return and solo features Following the military discharge of members Yonghoon and Kanghyun, Onewe returned with their third EP Planet Nine: Isotropy on April 17, 2024, resuming promotions through music broadcasts and various festivals and concerts. In addition to his promotions with Onewe throughout the year, Giuk featured in the singles "Back To You" by Aden, released on July 30, and "You Don't Love Me" by Divine, released on October 2, 2024. He is also featured on Divine's "You & Me" released on February 12, 2026.
Discography
Extended plays TitleEP detailsPeak chart positionsPhysical salesKORPeaks on the Circle (formerly Gaon) Album Chart: Psycho Xybernetics: Turn Over: Rise Waves: Psycho Xybernetics: Turn Over Released: January 28, 2023 Label: RBW Formats: CD, digital download, streaming56KOR: 7895Cumulative Sales of Psycho Xybernetics: Turn Over:
Rise Waves Released: November 15, 2023 Label: RBW Formats: CD, digital download, streaming33KOR: 6643Cumulative Sales of Psycho Xybernetics: Turn Over:
Singles
As lead artist TitleYearPeak chart positionsAlbumKORDL"Time Machine (2100)" ()2023 —Psycho Xybernetics : Turn Over"Scratch" ()179Rise Waves"—" denotes releases that did not chart or were not released in that region.
As featured artist +TitleYearAlbum"A Girl's Panorama" 2023MyMy"Back To You" (오늘 또 내일) 2024 rowspan="3" "You Don't Love Me" (틀린 말없이) "You & Me" (너 하고 나) 2026
Soundtrack appearances
As featured artist TitleYearAlbum"Promise" 2016The Miracle OST Part.2
Filmography
Television shows YearTitleRoleNotesRef.2017The Unit: Idol Rebooting ProjectContestantEpisode 1-72020Good GirlInvited audienceEpisode 82021Mama The IdolInvited audienceEpisode 1-2, 4-52022Great Seoul InvasionContestantEpisode 1-8
Radio shows YearTitleRadioNotesRef.2020-2021Day6's Kiss The RadioKBS RadioFixed guest, with Onewe Every 3 weeks from December 10, 2020 - October 14, 2021
Participating albums and Sound sources YearSongArtistAlbumLabelCreditedRef2022"Rockstar"RARERarenessBass"Congratulations"Moonbyul<Second World> Episode 3Studio JAMM, ShowplayBass2024"Like a Fool"Starlit of MuseRBWBass
Music production credits Giuk is the main writer and composer for his solo releases and co-writes/produces the vast majority of Onewe's output alongside the other members, as well a writing and producing for other artists. As of August, 2026, the Korea Music Copyright Association (KOMCA) has 138 songs listed under his name. All credits adapted from KOMCA, unless stated otherwise. +KeyIndicates single release +YearSongArtistAlbumLabelLyricsMusicCreditedWithCreditedWith2015"Butterfly, Find a Flower" (나비, 꽃을 찾다)M.A.S 0094Feeling Good DayModern MusicJeon Dawoon, Yoon Hyeoju, Jang Yoonseo2016"Feeling Good"M.A.S 0094M.A.S 0094, Jeon Dawoon"Starlight" (별보다 빛나는)Make Some NoiseIm Dohwan, M.A.S 00942017"Make Some Noise"M.A.S 0094, Lee Dong-gonJeon Dawoon, M.A.S 0094, Lee Dong-gon"Boobijuk Bibijuk" (부비적 비비적)M.A.S 00942019"Crazy & Crazy" (ㅁㅊㄷㅁㅊㅇ) (Prod. Giuk)OneusLight UsRBW EntertainmentRavn, LeedoJeon Dawoon"Ring on my Ears" (귀걸이가 나를 때리게)Onewe1/4Jeon Dawoon, Kanghyun"0&4" (공과 사)Kanghyun, YonghoonKanghyun, Yonghoon, Jeon Dawoon"Ring on my Ears (Remix)" (귀걸이가 나를 때리게)Jeon Dawoon"Kousikondou" (公私混同)Reminisce About AllKanghyun, Yonghoon, Hwang SungjinKanghyun, Yonghoon, Jeon Dawoon"Piasugabokuwobutuyouni" (ピアスが僕をぶつように)Hwang SungjinJeon Dawoon, Kanghyun"Love Me" (내가 처음 만져본 강아지)2/4Yonghoon"Regulus" (야행성)Kanghyun, HEUNGEULKanghyun, Jeon Dawoon"Feeling Good (2019 ver.)"Yonghoon, Kanghyun, Harin, DongmyeongJeon Dawoon, Yonghoon, Kanghyun, Harin, Dongmyeong2020"Q" (모르겠다고)