Kep1er was formed through the Mnet reality survival show Girls Planet 999, which aired from August 6 to October 22, 2021.

The show brought 99 contestants from China, Japan and South Korea to compete to debut in a multinational girl group.

[3] Kep1er was originally scheduled to debut on December 14, 2021, with their first EP First Impact, with pre-orders beginning on November 29.

[4] However, it was announced that the group's scheduled debut had been delayed to January 3, 2022, due to one of their staff members having tested positive for COVID-19.

[9][10] Gladys Yeo from NME gave the extended play three out of five stars, calling the EP an energetic six-track project record that makes for an enjoyable listen but falls short in fleshing out Kep1er's identity as an act.