It was initially released on May 22, for digital download. The single became an instant hit and quickly a number one hit on various online and offline charts. In order to promote the single, JYP Entertainment first released teaser pictures of each member in May , showing the Wonder Girls in their new "sexy image". Starting with Yeeun , pictures were released on 5 consecutive days, ending with Sohee 's pictures. Following the pictures, "So Hot" was previewed on their website. During this time, there were rumours that past member Hyuna would be returning to the group; JYP Entertainment confirmed that this was not the case.