SEE ALSO: Jaejoong, Yoochun's brother, and Gummy cheer on Junsu for his musical 'December'

Junsu tweeted, "B2ST's Kikwang and Dongwoon came out all the way to Sejong [Center For the Performing Arts] to watch 'December' in the middle of their busy schedules! Thanks so much~^^," revealing his unexpected friendship with the B2ST members through a backstage photo.

The dressing room shown above seems to have become a favorite hangout spot for celebrities who attend Junsu's concert, making fans wish they could also brush shoulders with him backstage.

Junsu also tweeted Dongwoon, "Whenever I do a performance, you always come with Kikwang.. Thanks, Dongwoon! If you do a musical, hyung will also come out to see it!!^^ For sure."

'December' will close its curtains in Seoul on January 29 and then move on to Daegu and Busan.