On April 27, 2024, SONRAY MUSIC announced that BUS would be debuting two sub-units named BUS5 and BUS7; BUS5 would be set to make their debut with BUS's 3rd digital single on May 1, and BUS7 on June 5 with the group's 4th digital single.[1] BUS7 would consist of the members Copper, Aa, Khunpol, Peemwasu, Alan, Nex and Thai.
The sub-unit officially debuted on June 5, 2024 with the digital single "Brother zone".
