BOL4 (also known as Bolbbalgan4 (볼빨간사춘기)) is a South Korean one-member act under Shofar Music. They debuted as a duo on April 22, 2016, with their first mini-album Red Ickle. On April 2, 2020, Shofar has announced that Woo Ji Yun has departed from BOL4, with An Ji Yeong to continue to promote under the duo's name, without any additional members