Simon D is one of my favorite Korean rappers and Zion.T is one of the best R&B singers out there (Korean or non). They were on a Korean music program Immortal Song 2, which has idols (and others) performing legendary songs. Obviously, I don’t have any sort of historical frame of reference for these songs, but it’s always fun to see idols (etc) I like performing songs that the audience knows. And this is no exception.
Also, for comparison, here’s what they’re usually like together, performing the song Stay Cool (off of Simon’s album: Simon Dominic Presents ‘SNL LEAGUE BEGINS’):