B1A4, standing for “Be The One All For One” as well as the members blood types (one type B and four type A), was a South Korean five-member idol group under the management of WM Entertainment. The group debuted on April 23, 2011 with the single O.K from their debut EP Let’s Fly, after being introduced to the public through a webtoon. At the time of debut, the group consisted of CNU, Jinyoung, Sandeul, Baro and Gongchan.

In 2018, members Jinyoung and Baro left the group and the agency, after the expiration of their contracts. As a result the group would continue on with the three remaining members. However, the group did not make a comeback until October of 2020, with the group’s long awaited return album entitled 영화처럼, or “Like a Movie” in English. In the meantime, the members, in particular, member Sandeul had been focusing on his solo career.

The group’s fandom name is BANA, and is written as 바나 in Hangul. According to a B1A4 fan Tumblr page:

BA represents B1A4 while NA represents the fans. When they’re put together, it means ‘we have fallen for each other’ which is 반하다 in hangeul. So basically it means B1A4 has fallen for their fans or the other way round.