SEE ALSO: Rainbow reveal mysterious pictures as possible comeback teaser images

Their agency DSP Media explained the four mysterious teasers on the 2nd, "Rainbow's 4-member project subunit Rainbow BLAXX has been formed with a 19+ rated sexy concept. They will make a comeback towards the end of this month."

This will be Rainbow's second subunit following Rainbow Pixie in 2011. Rainbow BLAXX will be showing the opposite end of the extreme from Rainbow Pixie, who had a cutesy image, with their mature sexy charms.

The four members will be revealed one-by-one starting on January 6 through their official YouTube channel!