Bolbbalgan4 (Hangul: 볼빨간 사춘기, also known as BOL4 or Blushing Youth) is a South Korean duo formed by Shofar Music in 2016. They appeared on Superstar K6 in 2014 before signing a contract with their current agency. The duo consists of Ahn Ji-young and Woo Ji-yoon. They debuted on April 22, 2016, with the single “Fight Day” from the mini-album Red Ickle. The duo went on a little break due to Ji Young’s music classes requirements in the first half of 2018.
Jiyoung and Jiyoon were both raised in Yeongju city, Gyeongsang, and were classmates. Since they were young they had dreamed of becoming singers. The name of their duo was built on the grounds that they wanted to make the kind of pure, honest music that can only be found in adolescence. Jiyoon portrays the “blushing” part of the name because she is often shy, while Jiyoung portrays “youth” because she acts like an adolescent girl.