WJMK (Hangul: 우주미키; short for Wuju Meki) is a four-member special project unit group between Cosmic Girls and Weki Meki created by Starship Entertainment and Fantagio Music. It is composed of four members: Seola, Luda, Choi Yoo-jung and Kim Do-yeon.
On May 2, 2018, Starship Entertainment and Fantagio Music announced the special formation of the project unit and released teaser images online. Promotional images were released throughout the month with bright color concepts. On June 1, their digital single “Strong” was released along with its music video.