The game begins in Decalburg after the Sticker Fest was forcefully ended by Bowser. Mario is woken up by Kersti and then proceeds to peel her off. After that, the Toads are shown to have been crumpled or attacked and are panicking over the ravaged festival grounds.
As each Toad is found and rescued, it is discovered that an entire portion of Decalburg has been rolled up, and all of the saved Toads are needed to unroll it. As soon as it is turned back to normal, Mario and Kersti are attacked by a gang of Goombas, in which the basic battle actions are taught. After the commotion, Mario and Kersti leave for the Warm Fuzzy plains, World 1-1.
Later, after Mario learns how to Paperize, he can pull off Decalburg Fountain to reveal the Green Toad that was crushed under the unrolling Decalburg. The Green Toad thanks Mario and officially opens up the Sticker Museum
Gradually, over the course of the game, the festival grounds are repaired.
The first area of Decalburg is the festival grounds, where the Sticker Fest takes place. At first, this site is ravaged and contains a very small selection of weak stickers, but gradually over the course of the game the Toads rebuild the grounds.
The next area is the residential area. It contains three houses, one of which is the house of the bullied Red Toad encountered over the course of the game. As he is rescued, paintings of those attacks appear in his house, and once all five appear, a friend of his will give Mario an HP-Up Heart.
The biggest area is the town center, where the Sticker Shop, Sling-A-Thing stand, and Sticker Museum are located. The Sticker Shop is one of five shops in the game and slowly gets more and more powerful stickers over the course of the game. The Sling-A-Thing stand is opened once Mario gets the Fan item from Bouquet Gardens. Also, once Mario gets multiple Things, a secluded stand opens up near the Sling-A-Thing stand. This stand sells the Things that Mario has lost and not gotten back again. The items are pricey, and the method is highly implied to be illegal.
To the left of the secluded stand is the Secret Door of Decalburg that it shares with The Enigmansion. The door serves as a portal between the two.