His first debut was in South Korea but failed. Then he went to Japan and his album became a hit because his single 'Only Human' was featured in 1 litre of Tears drama which made him quite popular. His name is Kang Yoon Sung and yes he is Korean.
Man, it's just not fair that some people have the talent to sing AND play an instrument at the same time. God this song is freaking so good. Great upload.