While foraging for donuts that are being tossed at the end of the day, Star encounters Mina Loveberry, a magical girl from Mewni who is Star's idol. Mina has been living as a homeless person on Earth. Star follows Mina and tries to train in her ways, which annoys Marco. At a park, when Mina announces she plans to take over the world, the people decide to hold a vote on whether Mina should rule, and Star is left to break the tie.
After having skirmished with a number of dangerous monsters, Star Butterfly arrives on Earth to live with the Diaz family. However, rather than living a normal life, Star continues on having to battle villains both throughout the universe and in their high school, although if only to protect her extremely powerful wand, an object which she is still confused with.