Perso ça m´a jamais effleuré l´esprit tellement j´étais dans le film et pourtant je vois cette critique partout depuis que le festival de Cannes.
L´explication une fois pour toute, lue sur koreanfilm.org :
" On the age difference between the two male leads, who in the film are supposed to be a similar age: Park said he on purpose cast the Oh Dae-soo character to look " a whole lot older" than the Lee Woo-jin character ( a comment which drew a playful glare from Choi Min-shik). He said he pictured Woo-jin as stopping his growth after the event we see dramatized in a flashback at the end of the film ( I´m trying not to give away spoilers here). He also wanted the effect of a younger man toying with an older one. Apparently he considered giving the Woo-jin character acne, but then decided it wasn´t necessary."