Rainbow has announced that they've signed on with Japan's Universal Sigma for their Japanese debut this September! Though they've yet to make their formal debut, the girls are already receiving much attention because they're the sister group and labelmates to KARA. The girls will be kicking off their official debut with a Japanese remake of their hit track, "A". According to DSP Media, the Japanese have taken a lot of interest into the fact that Rainbow's 'belly button' dance was banned on Korean broadcast networks. Representatives explained, "Because of the restrictions put on girl group outfits and choreography, we were unable to show everything we had prepared. Through their Japanese promotions, however, we will be showing off their 'belly button' dance." Rainbow is also currently preparing for their follow-up promotions this month, in addition to filming for their debut Japanese music video. Stay tuned to allkpop for more Rainbow updates! Source + Photos: Star News via Nate