When brothers Mario and Luigi end up with a big plumbing problem underneath their hometown in Brooklyn, they're suddenly sucked away and separated into a world beyond their wildest dreams.
Mario ends up in the Mushroom Kingdom, a beloved kingdom ruled by the beautiful and frondeur Princess Peach. But when they find out that the monstrous reptile named Bowser has taken a Power Star, along with holding Luigi and one of the princess's noble knights, (Y/n), hostage, it's up to Mario, Princess Peach, and their small but loyal sidekick Toad, to team up with their allies, and rescue their friends before Bowser takes over the world.
Mario and Luigi aren't the only children that Mama and Papa have. On a dark and stormy night, the couple finds a beautiful baby girl alone on the streets, known only as Froggy, raising her alongside Mario and Luigi. However, things get shaky when Froggy follows a strange caterpillar whom she befriended, and falls down a pipe, the brothers must venture into many kingdoms to rescue their little sister. However, things are not as they seem.