On June 11 at 6 PM, CSR (First Love) unveiled their new single "L'heure Bleue: Prologue," marking their return to full group activities after 1 year and 3 months. 

The album title, meaning "Blue Hour," represents the transitional period of being nineteen and conveys the challenges and growth during this phase. With this release, CSR aims to showcase their hopeful mindset and unchanging bright charm, overcoming their long hiatus.

The new single includes two tracks, "Nineteen" (HELLO) and the title track "Pretty Mob." 

"Pretty Mob" is an energetic hip-hop based song with a catchy rhythm and melody, expressing courage and hope even in dark times. The lyrics and rap highlight CSR's unique style and appeal.

The music video for "Pretty Mob," available on CSR's official channel, serves as a prologue to their nineteen-themed journey. It depicts girls navigating their personal struggles and embarking on a quest for happiness.

CSR will begin their comeback activities with a performance on SBS M and SBS FiL's "The Show" at 6 PM on June 11. 

Additionally, they are set to embark on a tour of five Japanese cities (Tokyo, Nagoya, Kyoto, Osaka, and Fukuoka) starting from June 29, followed by the release of their debut album in Japan in July.