015B, a South Korean music duo made up of brothers Jeong Seok-won and Jang Ho-il, stepped out in 1990 and enjoyed fame as one of the country's most popular groups of that period. Known for their 'guest singer system', the group have never have never appointed a permanent lead vocalist. Their debut album 015B was released in July 1990 via Jigu Records, marking the beginning of their career, and the duo quickly gained popularity with subsequent releases such as Second Episode (July 1991) and The Third Wave (August 1992), both of which achieved significant commercial success in South Korea. Throughout the 1990s, 015B turned their focus to various genres, including pop, K-ballad, synth-pop, electronica, R&B, and hip-hop. Notable albums from this genre-blending period include The Fourth Movement (August 1993), Big 5 (November 1994), and The Sixth Sense (May 1996). In the 2000s, the group continued to put out music with albums like the compilation Final Fantasy (May 2006) and the studio LP Lucky 7 (August 2006). Another compilation album, Anthology, followed in April 2018, along with a series of yearly compilations titled Yearbook, beginning in 2019 and with Yearbook 2024 arriving in 2025.