Kep1er is a multinational group that includes nine members from Korea, China, and Japan. After being put together on the Mnet competition show Girls Planet 999, which aired its finale in October 2021, they debuted on 3 Jan. with their EP First Impact, which features their lead single "Wa Da Da." Yujin, Mashiro, Xiaoting, Chaehyun, Dayeon, Hikaru, Huening Bahiyyih, Youngeun, and Yeseo make up Kep1er, which is named after the German astronomer Johannes Kepler.