A kid finds out her magical girl idol might be coming back, except she's the only one who knows what that actually means. The entire friend group mobilizes not to celebrate, but to investigate, because they've earned the right to be suspicious. Yuu gets to be the one person in the room who understands the cost of that comeback, and the show trusts you to feel the weight of that alone.

Two months have passed since Creamy Mami's final concert, and whispers are circling that the idol is planning a comeback. Adding to the surprise, Tachibana kicks off something called "Project M," which appears to be tied to Mami's return. Once news of a new Mami concert reaches the public, Yuu refuses to believe it. Together with Megumi, Toshio, Midori and Kidokoro, Yuu hatches a plan to find out what is really going on. The OVA opens with a lengthy recap of the original series before moving into this new story, blending comedy, fantasy, romance and magical girl adventure.