The long-awaited new installment of the "Mario & Luigi RPG" series after 9 years. The story takes place in the "Koleankutaru Continent," a different world from the Mushroom Kingdom. Mario and Luigi will embark on adventures to various unknown islands floating on the sea. To venture in the Koleankutaru Continent, the two brothers must cooperate closely. Particularly, after mastering the special cooperative skill called "Brothership Action," they will be able to explore various areas.