"The Irregular at Magic High School The Movie: The Girl Who Summons the Stars" is a feature-length anime film set in the same universe as the original series, expanding on its magical science-fiction world. The story takes place after the events of the first season and the "Visitor Arc," focusing on Tatsuya Shiba, a technically inept but highly skilled magician, and his sister Miyuki, a prodigious magician with exceptional abilities. The narrative centers on a new conflict involving advanced magical technology and interstellar intrigue.

The film introduces a mysterious artifact known as the "Astronomical Artifact," a relic of ancient magic technology capable of manipulating celestial phenomena. The artifact becomes the target of a covert organization seeking to exploit its power for global dominance. Tatsuya and Miyuki are drawn into the conflict when their friend, Honoka Mitsui, is kidnapped by the organization due to her unique connection to the artifact. Honoka possesses latent magical abilities tied to the artifact, making her a key to unlocking its full potential.

As Tatsuya and Miyuki investigate, they uncover the organization's plan to use the artifact to summon a massive meteorite, threatening catastrophic destruction. The siblings, along with their allies from First High School, must navigate a web of political intrigue, advanced magical combat, and scientific experimentation to thwart the organization's scheme. The story highlights Tatsuya's strategic brilliance and combat prowess, as well as Miyuki's mastery of magic, as they work together to protect their friends and prevent global disaster.

The film explores themes of loyalty, the ethical implications of advanced technology, and the bonds between siblings and friends. It maintains the series' focus on intricate magical systems and high-stakes action while introducing new elements of interstellar magic and ancient lore. The narrative builds on the established dynamics between the characters, particularly Tatsuya and Miyuki's close relationship, while expanding the scope of the series' world-building. The film concludes with a resolution that reinforces the protagonists' roles as defenders of their world, setting the stage for potential future developments in the franchise.