Bolbbalgan4

Bolbbalgan4, also known as BOL4 or Blushing Youth (赤頬思春期), is a South Korean musical act formed by Shofar Music in 2016. They appeared on Superstar K6 in 2014 before signing a contract with their current agency. BOL4 was originally a duo consisting of Ahn Ji-young and Woo Ji-yoon. They debuted with the single "Fight Day" from the mini-album Red Ickle on April 22, 2016. The first syllable of the Korean word sachungi "puberty" is pronounced the same as the Sino-Korean numeral four (sa), and accordingly the group name is sometimes shortened to BOL4.

The duo went on a temporary hiatus due to Ahn's music classes requirements in the first half of 2018. Bolbbalgan4 signed with King Records and debuted in Japan on June 5, 2019, with the mini-album Red Planet (Japan Edition).

On April 2, 2020, Shofar Music announced that Woo Ji-yoon had left the duo, and Ahn Ji-young will continue to promote as Bolbbalgan4 as a solo act.

Formation
Jiyoung and Jiyoon were both raised in Yeongju, North Gyeongsang Province, and were classmates. They had previously competed Superstar K 6 in 2014. 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.

Current

 * Ahn Ji-young (안지영) – main vocals

Former

 * Woo Ji-yoon (우지윤) – guitar, rapping, backing vocals

Headlining concerts and tours

 * BOL4 1st Solo Concert "Red Planet" (2016)
 * BOL4 1st Concert in Taipei (2017)
 * BOL4 2nd Solo Concert "Imagine" (2017-2018)
 * BOL4 3rd Solo Concert "Travel" (2018)
 * 2019 BOL4 Spring Solo Concert "Flower Energy" (2019)
 * 2019 BOL4 Asia Tour "Blossom" (2019)
 * 2019 BOL4 Tour Concert "Two Five" (2019)
 * BOL4 (赤頬思春期) Japan Live Tour 2020 "Love" (2020)
 * BOL4 Concert "Seoul" (2022)
 * 2023 BOL4 Concert in Taipei (2023)
 * BOL4 Concert "Love.zip" (2023)
 * 2023 BOL4 Asia Tour "Love.zip" (2023)

Showcase

 * BOL4 (赤頬思春期) 1st Live Showcase 宇宙をあげる～ (2018)