Hae Soo attended the prestigious Dankook University, where he studied theater and film. It was at the university that he began to actively act in the theater and fell in love with the stage. The theater became his first real acting school - before he got into television, he performed on stage for many years, and many critics still consider him a "stage actor".

University life is noisy, youthful, and rushed. But he always seemed a little out of place. Hae Soo didn't stand out, but he was instantly memorable.

From the 204 auditorium of the theater building, every evening, one could hear lines spoken aloud and the muffled voice of a guy who seemed to be rehearsing not for an audience, but for someone who had long since left. He stood alone, in a simple sweater, with a text in his hands, reading not a dialogue but a confession. He was focused, his eyes looking at the text, as if he were trying to remember something.