July 25, 2012 08:45 AM EDT
jang / Credit: suk
On July 24, he posted on his Twitter "Please show much love for 'Love Rain' in Japan," along with a photo.
In the revealed photo Yoona and Jang Keun Suk are smiling brightly into the camera.
Those who saw the photo commented "'Love Rain' is going to do well in Japan," "The best Korean Wave stars have gathered," and "Prince and princess are together."
Photo Credit: Jang Keun Suk Twitter