YoonA cheered on her fellow Girls' Generation member Hyoyeon's solo stage with "Mystery"!

On December 3, YoonA posted the photo of the two below with the message, "Mystery. #Hyoyeon unni's first solo track #Mystery #Pretty Cool Doing Well #Yongstagram." It looks like YoonA visited Hyoyeon in the waiting room of MBC's 'Show! Music Core' to give her some support.

How sweet! Watch Hyoyeon's performance if you missed it!