With their mysterious comeback coming in the days ahead, f(x)'s Luna posted a mirror photo of herself on Friday, October 16 on Instagram.

The picture was taken in what seems to be f(x)'s practice space in SM Entertainment's headquarters. Taking the mirror photo, Luna wore all black from top to bottom along with a hat. She is making half of a heart with one of her hands as she points to Amber who is in the back of the practice room, eating something. 

"Koala, is it good?," she playfully captioned on her photo.

f(x) will be making their comeback soon as another teaser or hint on their comeback is set to drop on October 21.