For the next two years, Yoo didn't appear in any new films, because "Natural City" took an unusually long time to progress from shooting to a commercial release. He then appeared in three works in 2003: "Natural City" (which bombed, despite its big budget and special effects), the horror/suspense film "Into the Mirror", and Park Chan-wook's acclaimed "Oldboy". Yoo's memorable role in the latter film as a wealthy eccentric fixated on revenge would make his face well known to international audiences.