Their group name H1-Key is pronounced and inspired by the word "High Key" and the aim for "confident" and "healthy beauty".

[3] Sitala, daughter of the late Thai actor, singer and producer Sarunyoo Wongkrachang, was a trainee under Lionheart Entertainment.

[6] On November 23, 2021, Yel was announced as the group's first member through a self-choreographed cover video of "Bad Habits" by Ed Sheeran.

[8] When GLG unveiled the group's Thai member Sitala in November 2021, various K-pop fans in Thailand called for her removal, as her late father was a known supporter of the People's Alliance for Democracy, a military tyranny that ousted two democratic-elected civilian governments in the 2006 and 2014 military coup d'états.

[9] On December 21, 2021, it was announced via social media that the group make their debut with their first single album, Athletic Girl, with the title track of the same name.

[15][16] On June 7, it was announced that the quartet would be releasing their first maxi single album titled Run on July 6, with the addition of a new member, Hwiseo.

[19] In June 2023, members Riina and Hwiseo were participants in the Mnet girl group survival show Queendom Puzzle.