On July 10th Starship Ent tweeted this picture captioned, "SISTAR to make a comeback this summer! Mark your calendar, it's 21st, July! Hope you are all looking forward to it :)"
This new song will be produced by Rado and Choi Kyu Sung (they've worked with Troublemaker, g.o.d and more).
apparently, SISTAR went to Saipan to film the video for this comeback!