Their second mini album '[Under Cover]: Because I Want You to Be Mine, Be Mine' will be released on the 17th of May at 12PM KST. 들린다면 (IF YOU HEARD) is a song dedicated to their fans co-written by A.C.E.
Sources: official A.C.E
The teaser for the comeback is at the end of the video. My fave nugus are back! It's been a long time since their last comeback. They were supposed to comeback last September, but it got delayed and then they went on tour.