The hero is given an opportunity to either destroy the Dark Curse or provide them with a new face and body. The Sage quickly traps the Dark Curse, and explains its history to the hero: it was once a normal Mii, rejected due to having a boring face, which they then decide to get rid of, and they faded away into a soul of hatred, malice and evil, which became the Dark Curse. After the Darkest Lord is defeated, the Great Sage is free. Afterwards, the Darker Lord steals the faces of six heroes, evolving into the Darkest Lord for the fight with the last four members. The hero and their team are then prompted to split up to fight the Darker Lord. Upon reaching the top of The Sky Scraper, the heroes go to the Otherworld for the final showdown against the Darker Lord. The hero and their team track down the Darker Lord through the lands of Powdered Peaks, Peculia and Nimbus, before reaching the Darker Lord's Domain in The Sky Scraper, fighting previous bosses along the way. Enraged, the Dark Curse tries to possess the player's Mii, until the Great Sage intervenes and becomes possessed instead, becoming the Darker Lord. The team fights the Dark Lord, and upon defeating them, the heroes discover that the Dark Lord was a common Mii possessed by a small blue wisp known as the Dark Curse. The hero is tasked with saving all of their friends, with some help from the Great Sage. Upon arrival, the Dark Lord attacks again, stealing the new companions, but failing to steal the hero's powers. After retrieving their faces, the Fab Fairies open the door to Karkaton, and the team head out. Before they can open the door, the Fab Fairies have their faces stolen by the Dark Lord.

The hero is tasked with saving the three Fab Fairies of the Realm, who provide the team the way to the Dark Lord's castle in Karkaton. The team continues to the Realm of the Fey, where the Dark Lord attacks again, stealing the hero's companions and their character class again, prompting the guardian to provide a new group of character classes. After the guardian provides the hero with new powers, they head out through Neksdor, meeting three new companions and the Genie of the Lamp. Afterwards, the team enters the kingdom of Neksdor, only to be attacked by the Dark Lord, who steals the protagonist's companions and renders the protagonist without a class. Along their journey, the player creates more companions, meets the Great Sage, and reaches Greenhorne castle, continuing the quest after the Dark Lord steals the faces of the King and the Princess. The protagonist chooses a character class and is sent on a journey to stop the Dark Lord. The game begins with the main protagonist, a Mii of the player's choice, arriving in Greenhorne Town, which is soon attacked by the main antagonist, the Dark Lord, who wields the ability to steal faces from Miis and use them to control peaceful creatures, turning the creatures into monsters. The Switch remaster also includes a horse that can help in combat which was not included in the original 3DS version, alongside a secret final dungeon after the Tower of Dread, the Tower of Despair. The Nintendo Switch remaster also introduces a new makeup and wig feature which allows players to further customize their in-game characters, including options not available on the console's Mii Maker application. The game supports Nintendo's line of Amiibo figures, which allow players to use unique cosmetics on their Miis.

Miitopia supports the ability to import Miis and their trait settings from Tomodachi Life, as well as from a player's friend list.

Similarly to Tomodachi Life, the relationships between Miis outside of combat affects the game: for example, Miis not getting along with one another can make combat more difficult. Playable characters are created with Mii avatar and have certain personality traits which influence their role in combat. Miitopia is a role-playing video game with life simulation elements, starting with standard character classes or 'jobs' such as warriors and mages as the game progresses, more classes appear. Players' stats and actions can be accessed from the 3DS's bottom screen. Two Mii characters engaging in the game's combat sequence on the 3DS version.

Miitopia wiki