KELT9b

V uploaded their first dance cover as DMZA on their company's Youtube channel, revealing the group had a name change. On August 16, 2019, DMZA officially introduced their first member: Minju. However, two other members were already known to the public without official introduction.

The group account was following the personal accounts of two other members: Russian member Senia and Japanese member Hime. On September 2, 2019, the second official member introduction took place. This time, they revealed Joonee through a solo vocal cover.

On September 11, 2019, Ayeon was introduced, followed by Chinese member Ginny on September 28. On November 19, 2019, Ruby was introduced, followed by Lasha on November 30, 2019, but her profile was deleted within the same day. Her performance video on their YouTube remained, however.

As of January 2021, the video has been privated. Sometimes in 2020, Ayeon, Ginny, Hime, Senia, Ruby, Gayoung, Hayan, Taeeun, Jimin, and Joonee have left the group lineup due to the delay of their debut which was caused by the COVID-19 pandemic. On February 29, 2020, Siyeon was introduced.

On April 8, 2020, Youngchae was officially introduced. On December 29, 2020, they announced that Lasha and Siyeon had left the group due to unavoidable circumstances. In an interview released on February 1, 2021, US Media Group revealed that their debut, which was initially planned for 2020, was delayed due to the COVID-19 pandemic.

However, they have now been confirmed to debut in the second half of 2021 with the remaining members while auditions are open for new members. The agency stated that they will plan to debut DMZA as a large girl group with many members and that they are preparing a concept that has not been seen in exiting girl groups yet. On March 1, DMZA slowly began revealing member's official photoshoots, suggesting their debut date is near.

Unfortunately ahead of their debut plans, member Jinseo left, leading to the reveal of Euijeong on March 26. On November 23, they revealed a new member, Sunwoo (later known as Lua). On November 28, they revealed a new member, Chaerin, through a dance cover video, releasing also her profile on the group's fancafe along with some pictures of her.

On May 1, they revealed their official group name, KELT9b. On February 2, it was announced that the group will release a pre-debut single, "Welcome To My World" on February 7. On February 8, US Media Group announced that Youngchae had left the group.

On November 13, it was announced that the group will debut on November 23 with the digital single "Uncrushable". However, the release was teased as a mini album and ended up being a digital single only.