The song here is performed by Jo Sung-Woo, a very popular actor in South Korea, appearing in a great many films, as well as stage, starring in such musicals as Man of La Mancha, Les Miserables and a musical adaptation of Doctor Zhivago. In fact, his breakthrough role came in 2004 with Jekyll & Hyde. He did his compulsory military service -- which I assume is when this video took place -- after which he reprised his Jekyll & Hyde role.
I was going to say that it's nice to write about Korea and have it about singing and dancing and musicals and all happiness and light...but then I remembered that this is Dr. Jekyll and Mr. Hyde, so -- well, it's a nice song, especially when you don't know what it's really about.
And P.S. He's quite good.