In the movie, Usagi and her friends are enjoying their winter vacation when they are suddenly caught in the midst of a fierce snowstorm that blankets the city in snow. As they try to make their way home, they come across a strange woman named Kakeru who seems to have a mysterious connection to the snowstorm.
As it turns out, Kakeru's girlfriend Himeko is an astronomer who has discovered a strange comet, which is actually the magical crystal that Queen Kaguya is after. With the help of her minions, she plans to steal the crystal and use its power to cover the Earth in ice, plunging it into an eternal winter.
Usagi and her team must spring into action to stop the Snow Queen and protect the planet. With the help of the Legendary Ultimate Scout Power, Sailor Moon takes on Queen Kaguya in an epic battle that will determine the fate of the Earth.
Along the way, Usagi also learns an important lesson about the power of love and friendship, as she grows closer to Kakeru and Himeko and discovers that their love for one another may be the key to saving the world.