Episode 4 S01 E04

Bae Yong-jun (as Kang Joonsang / Lee Minhyeong) Choi Ji-woo (as Jeong Yoojin) Park Yong-ha (as Kim Sanghyeok) Park Sol-mi (as Oh Chaerin) Lee Hae-eun (as Gong Jinsook) Ryu Seung-su (as Kwon Yonggook) Song Ok-suk (as Kang Mihee) Jeong Dong-hwan (as Professor Kim Jinwoo) Kim Hae-sook (as Yoojin’s mother) Jang Hang-seon (as Supervisor Kim) Jung Won-joong (as Teacher Park Jeongo) Ha Jae-yeong (as Jeong Hyeonsoo) Lee Hyo-choon (as Sanghyeok’s mother)