Nadine was 18 and Erwin was 30
That is, the actors' ages at the time of filming. Is there something about Koreans that lets them get away with playing teenagers at age 30? Keiko Agena, who played Lane Kim on GILMORE GIRLS, was eight years older than Alexis Bledel, who played her best friend Rory on the show, even though the characters were the same age and in high school.
Do these Korean actors look plausibly like teenagers to other Koreans?
(Love this movie BTW)