A boy named Rio is enjoying Gunpla Battle in the new Internet service known as the Gundam Metaverse Project. After installing a login set in his room at home, he dives into the Metaverse, together with the Lah Gundam he created with this day in mind.

The true identity of Rio's Gunpla Battle master, Mask Lady, is his real-life Gunpla building mentor Seria Urutsuki. Having learned of the connection between Seria and Maria, Rio joins a subjugation mission to clear the worries from his mind. Here he encounters a black Gundam.