GEM (Girls Entertainment Mixture) is a Japanese pop idol group and the third group under iDOL Street. 2012-2013: Formation GEM was first introduced at a SUPER☆GiRLS concert on December 25, 2012. The starting line-up consisted of 11 members, but throughout 2013 the line-up was changed with four members leaving and three joining, leaving them with a final line-up of 10 members by June 2013. On July 27, 2013, they released an indies single titled "Speed Up / Do It Do It".