Moon Sua revealed through her official Instagram that she selected Christopher's "moments" as the background music while sharing memories of the late Moonbin. Moon Sua said, "Brother, it's been a while. Are you curious about what song I brought this time? I was thinking and wanted to choose a song that also holds memories of you." She continued, "You liked this song, right? The lyrics are really nice too. It's exactly what I want to say. I hope my sincerity reaches you." She also said, "The weather has gotten much warmer. I'm working hard preparing for my comeback, and it's my first full-length album! Somehow, I feel like you would give me a lot of feedback if you saw it, so I'll work hard thinking you're watching. When we meet, please praise me. Okay? I miss you a lot and love you."

Billlie will make a comeback on May 6 with their first full-length album, the collective soul and unconscious: chapter two. The album consists of 12 tracks, including seven new songs such as the title track "ZAP," "$ECRET no more," "WORK," "TBD," "B'yond me," "SOUPASTA," and "OFF-AIR," four remix tracks, and the Korean vocal version of "DOMINO ~ butterfly effect," which was previously released in Japanese. The album focuses on building Billlie's expanded musical world (B-side).

Meanwhile, Moonbin passed away on April 19, 2023. Born in 1998, Moonbin entered the entertainment industry in 2006 by appearing in TVXQ's "Balloon" music video and worked as a child actor in the 2009 KBS 2TV drama Boys Over Flowers. He later debuted in 2016 as a member of the Fantagio boy group Astro.