No worries – she’s not cameoing in the drama and appearing in a completely tangential story line. She’s going to be participating in the OST for the drama, singing “My Only One.” This will be her first OST song after four years, and her first drama OST song. In the past, she only did songs for movie OSTs.
I’m curious to hear it, though I hope it doesn’t get overused to highlight every dramatic/emotional moment. That would just kill my love for her music.