 On January 26, 2012, it was announced that Lee-seul and JoA were leaving the group and would be replaced by Min-hee and Hyo-eun for their first comeback track "UFO".On July 11, 2013, Stellar released their third digital single "Study" which, and chart in the top 100 their first time.On February 12, 2014, Stellar released their first extended play "Marionette".