The Lush is a (mostly) vocal trio consisting of J.mi/J.美, Mini (Minhee) and Sarah (I don't know if it is true, but I heard they are formal vocal trainers and were part of the Korean's Army Choir). They debuted under Oscar Entertainment in 2013 with the single Miserable. The mv is no longer available on any official channels, but someone did upload the mv with English subs.
They had a comeback in 2017 with I Belong To You, which is available on Spotify and can be listened to here: