On the September 18th broadcast of KBS '1 Night 2 Days', Lee Seung Gi and Sung Si Kyung joined forces and sang their hearts out with a sweet harmony, touching viewers. Sung Si Kyung began to sing Seung Gi's song,�'You Were an Impression' and 'Perfume'; Lee Seung Gi followed to join in harmony shortly after. The duo's sweet harmony and beautiful melodies caused viewers to slowly close their eyes and sing along. Along with Sung Si Kyung, Hyun Chul, Koyote and B2ST also were surprise guests on this episode. Source & Image: Naver