Ji-woo, an outcast at a prestigious private school, meets Hak-sung, the school janitor who is actually a mathematical genius who defected from North Korea.
Ri Hak-sung
Han Ji-woo
Ahn Gi-chul
Kim Geun-ho
Park Bo-ram
Tae-yeon
Park Pil-joo
Professor Oh
Bo-ram's Mother
Ji-woo's Mother
Korean Teacher
NIS Agent
Student 5
Ui-joon
Principal
Hanbok Teacher
Ddal-bong
Missionary
Young Professor Oh
Euler instructor
Doctor
