Following the storyline of the second video game, the second series delves into the mysterious lost land of Mu, an ancient civilization that has faded into myths and legends. As UMAs, unidentified lifeforms, merge with humans to seek the legendary treasures of Mu known as ooparts, Subaru and War-Rock find themselves facing peculiar foes. Their path crosses with Doctor Orihime, a professor who tasks them with a mission to locate the ooparts and thwart the UMAs' plans. With the aid of these powerful artifacts, Rockman gains the ability to transform into Thunder Berserk, Fire Dinosaur, and Green Shinobi, unlocking new potentials in the battle against evil.