On Top

In 2020, Rainbow Company (later known as Rainbow E&M) created Future Idol, an idol development project for the purpose of debuting various project idol groups throughout 2021 through its project, known as 'Future Idol Asia'. On April 29, 2021, Future Idol Asia introduced On Top and its members through their YouTube, FutureIdolTV. While pre-debut, On Top was one of several teen idol groups who performed a showcase at YES24 Live Hall on May 23, 2021 as part of the 'Future Idol Debut Project' event.

On December 3, 2021, On Top revealed the teaser for their debut digital single, "상관없어. The single was released on December 10, marking their official debut as an 11-member girl group.