Episode 5 S01 E05

Lee Jung-shin (as Kang Shin-Woo) Seo Ji-hoon (as Young Kang Shin-Woo) Lee Yul-eum (as Han Ji-Soo) Lee Tae-seon (as Shin Joo-Hwan) Cho Lee-hyeon (as Baek Na-Hee) Min Do-hee (as Jang So-Ra) Lee Joo-hyung (as Choo Geun-Deok) Kim Sun-young (as Shin-Woo's mother) Park Han-sol (as Kim Yun-jeong) Ko Kyu-phil (as Mozart student's Head Teacher)

time travel high school based on comic romance teacher hidden identity