left -> right: denise, dita, soodam, jinny, lea
Denise Kim and Jinny Park are both former YG trainees (the latter competed on Produce 48 after leaving). Lea (Ogawa Mizuki) competed on MixNine as an independent trainee and is also a former Skarf member under the stage name Hana. Dita is Indonesian, from Bali. Interestingly, all the members still have and maintain their individual instagram accounts.
source: secretnumber.official, SECRET NUMBER (2)