KEP1ER was formed by CJ E&M through the show Girls Planet 999, which aired in 2021. The show aimed to create the best girl idol group through competition among participants.
Initially, KEP1ER had nine members. However, in mid-2024, two members, Kang Ye-seo and Sakamoto Mashiro, were no longer part of the group after they did not renew their contracts. This caused the group formation to change to seven members.
KEP1ER announced that they will comeback with a 7-member formation and release their sixth mini album titled "TIPI-TAP" on November 1, 2024.