Bolbbalgan4 (also 볼빨간사춘기, BOL4) is an indie female duo (Ahn Ji Young & Woo Ji Yoon) formed by Shofar Music. They participated on Superstar K 6 in 2014 and signed a contract with their current company, but didn't make their debut until 2016. They officially debuted with the mini album RED ICKLE on April 22, 2016. As of April 2, 2020, Shofar Music has announced that Bolbbalgan4 will be shifting to a one-member lineup as Woo Ji Yoon sets to leave the group. Ahn Ji Young will be continuing as a soloist under the group's name.