Kim Young Guk was the lead vocalist for the Add4 backed album, Where Are You (그대는 어데로).
Apart from this release, and its subsequent reissues, there is not a lot known about the singer. Just like the Add4's lead singer Seo Jeong Gil, he appears on a couple of various artists releases, usually contributing one or two songs.
However, there are three known releases which contain the singer's photo prominently on the front sleeve.
First of which features a colourised photo of the singer on the front sleeve and is a various artists release. This record was most likely released in the mid 1960s.
The second known record uses the same black and white photograph that can be seen on the back sleeve of the Add4 album on the front cover. This release is most likely a promo only release and is assumed to be from some time between the late 1960s and the early 1970s, judging by the Universal Records' label shape.
The third record appears to be a split album, and features a much older looking Kim Young Guk on the front sleeve.
Little is known about these two releases and there are almost no audio recordings of the songs online.