CSR (첫사랑/Cheos-Sarang, formerly known as 05class) is a 7 member girl group under POPMUSIC and RBW Entertainment Japan. They debuted on July 27, 2022 with the mini album Sequence: 7272. The girl group’s concept is a class of young girls who were born in 2005. The group consists of: Sua, Sihyeon, Yuna, Seoyeon, Duna, Geumhee, and Yeham.