From their official channel, the MV for "UPPER DISCO"…
UUG(2) are only background dancers in this MV, as they were when they all performed this song at SATOYAMA&SATOUMI…
viewtopic.php?p=220995#p220995…which makes sense since that was probably around the time they recorded this MV. As such, we still don't have a real answer on if/when/how UUG(2) will be integrated into the group.
Also, is it just me or are the vocals oddly muted in this song? It's bad enough that it's difficult for me to listen to.