Mega Man Volnutt, aboard the airship Flutter with Roll and Barrel, retrieves a large blue refractor from an ocean ruin—only for engine trouble to force a crash landing on Kattelox Island. The island quickly proves eventful: the pirate Bonne family has arrived deploying giant mechanical weapons in search of the island's legendary treasure. Mega Man steps in to defend the city, defeating Tron Bonne, Bon Bonne, and eventually Teisel Bonne. Mayor Amelia reveals the danger: ancient legend warns that uncovering the island's secret treasure would bring disaster. Meanwhile the ruins are growing more active, and Reaverbots are appearing in greater numbers.