An ancient civilization called Mu disappeared long ago. Traces of it survive in myth and legend as UMAs, unidentified lifeforms, and these beings start merging with humans so they can hunt for Mu's treasures. Those treasures are the ooparts, powerful artifacts that could bring Mu back. Subaru and his partner War-Rock run into a string of strange enemies, and then a professor named Doctor Orihime sends them out to find the ooparts and stop the UMAs. With the ooparts, Rockman can take on new forms such as Thunder Berserk, Fire Dinosaur and Green Shinobi. The story picks up from the second video game in the franchise, and the adventure pits Rockman and Harp Note against new enemies with new powers.