クリィミーマミがファイナルステージを最後に引退してから2か月後、森沢優は普通の小学生として日常を過ごしていた。そんなある日、マミのカムバック騒動が起こる。マミの正体を知る優と俊夫は絶対にあり得ない話だと笑うが、パルテノンプラ社長・立花慎悟が極秘裏に進めていた…。
Two months after Creamy Mami's final concert, rumors began to spread that Mami was making a come back, and if that wasn't surprising enough, Tachibana starts a "Project M" and that seems to have something to do with Mami's come back. As word of Mami's concert reaches the public, Yuu dosen't belive it. Yuu, Megumi, Toshio, Midori, Kidokoro make a plan to get to the bottom of it.
