The members of B2ST divided into�teams of two for their "Welcome to B2ST Airlines" concert, and they recently announced that the solo songs each pair had come up with will see an official release very soon. The three duet tracks will also be joined by a full version of "Lights Go On Again", starting from December 21st. The first up to bat is unit duo�Doojoon and Dongwoon. At 11 AM KST, a teaser video for their ballad track, "When the Door Closes," will be revealed, followed by the full digital track release at 5 PM KST. The teaser video features footage of the two personally producing the song with all of their care in response to the support they've been receiving from their fans. [UPDATE: the teaser video has already been unveiled, so check it out below!] Source: Sports Chosun via Nate