Old Days is a documentary about Park Chan-wook's original masterpiece, Oldboy. It was created for Plain Archive's Blu-ray release and first screened at the Jeonju International Film Festival.

A little girl who lost her father to a serial killer 15 years ago awaits for his release, while a suspecting detective follows the killer upon release.

Jun-shik, who works for Tatsuo’s grandfather’s farm while Korea is colonized by Japan, dreams about participating in the Tokyo Olympics as a marathon runner. Tatsuo also aims to become a marathon runner, so the two become rivals. But the war breaks out and they both are forced to enlist in the army. Tatsuo becomes the head of defense in Jun-shik’s unit and he devises a scheme but fails. Jun-shik and Tatsuo are held captive by the Soviets. They run away but soon are captured by the Germans and forced to separate. In 1944, they meet again on the shores of Normandy.