Lee Joon-gi was 21 in The Hotel Venus when he played the character 'Boy'.
That was over 20 years ago in 2004.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 42, and has starred in 8 movies in total, 7 of those since The Hotel Venus was released.
In The Hotel Venus, I think Lee Joon-gi looks: