Marinette's class is headed to New York, the city of superheroes, for French-American Friendship Week.

On school break, Marinette heads to Shanghai to meet Adrien. But after arriving, Marinette loses all her stuff, including the Miraculous that allows her to turn into Ladybug!

Miraculous holders from another world appear in Paris. They come from a parallel universe where everything is reversed: the holders of the Ladybug and Black Cat Miraculouses, Shadybug and Claw Noir, are villains, while the holder of the Butterfly Miraculous, Betterfly, is a superhero.

To save the future from a terrible fate, Marinette becomes Chronobug and teams up with Bunnyx to defeat a mysterious opponent who travels through time.

Kagami drags Marinette to Tokyo to help the Stellars defeat a new supervillain, but Marinette soon realizes her friend has another, untold reason for this trip to Japan.