Ryu Sera, formerly of 9Muses, covered ''Psycho'' by 9Muses.
Sera took the time to post a cover of Psycho by Red Velvet. In the video Sera is seen wearing a hanbok while she sings over the instrumental which mainly is a gayageum (a traditional Korean string instrument). She also includes elements of pansori in her singing, resulting in an amazing, sweet cover.
Check out here cover of Dreamcatcher's "Deja Vu" as well.. it's fantastic!