Behind-the-scenes snaps for Sunday’s episode of “Running Man” featuring the cast from the upcoming period drama “Scarlet Heart: Ryeo” have been released.The photos show Lee Joon-gi, Hong Jong-hyun and Kang Ha-neul, who all play princes during the Goryeo Dynasty in the new SBS drama, shooting toy arrows and eating traditional Korean snacks. “Scarlet Heart: Ryeo” is a time-slip-themed series drama, inspired by Chinese novel and TV series “Scarlet Heart” and set to premiere on Monday.By Son Ji-hyoung ()