That's Shin Jung-Hyun and the Yup-juns playing in a 1975 movie titled "Miin", or 'Beautiful woman'. According to this review, it stars Shin Jung-hyun and Kim Mi-yeong, and was directed Lee Hyeong-pyo. In the film the band, and Shin, play struggling musicians who are helped out by a young woman who Shin fantasizes about (leading to several fantasy scenes where he admits his love to her). I had no idea Shin had made a movie. Too bad it came out just before he was arrested during the "marijuana crisis" of 1975, along with dozens of other musicians, and forced to stop performing.
Prompted in part by this interview with Mark Russell, (funny how the English version leaves out all the interesting bands and singers mentioned in the interview, as (perhaps?) it's assumed foreign readers wouldn't know who they are) I've been listening to Shin Jung-hyun and Kim Jung-mi a lot the past few days. A few tracks from Kim Jung-mi's 1973 album Baram ('wind') can be heard here (just be certain to turn off the two tracks you don't want to listen too, as all three players start playing automatically). The first, unnamed track is 'Baram,' followed by 'Areumdaun Gangsan' and 'Dangsini.' They're all good examples of Kim's psychedelic folk music at the time. It's too bad there isn't more like it today.
Oh, and thanks to orienkorean, who uploaded the Miin video above (along with 1500 other Korean rock/indie/electronic/classic rock videos). Thanks to him, you can also enjoy a 1971 movie clip with the Pearl Sisters (more of them here) and Kim Chu-ja, as well as twovideos of Kim Jung-mi, among many others.