Rustica is a wizard that resides within the Western Country. An elegant but leisurely gentleman. He travels around the world with his disciple, Chloe, looking for his lost bride. He does not know how to care for himself, so Chloe often takes care of him instead. 

A world where witches and humans coexist. There are five countries on the continent that is the center of the world, and their land patterns and personalities vary from country to country. In this world, a big moon floats in the sky, and people call it the "Great Calamity" that attacks the world by exerting its mighty power.
 
This is the story of the wizards who fight the Great Calamity.

On a moonlit night, Akira Masaki finds herself in a magical world where wizards and humans coexist. Every year, they must face an enormous, deadly moon that attacks the planet. Their only hope lies with the Wizards of the Sage, appointed to fight the supernatural threat. But Akira soon discovers she wasn’t summoned by chance—she was chosen to lead them in battle. 
 
(Source: Crunchyroll) 
 
Note: Animation project for Mahoutsukai no Yakusoku announced during the stream event "Mahoutsukai no Yakusoku 4-Shuunen Kinen Tokuban: Mahoyaku 4-Shuunen Goukon" held on Nov 12, 2023.

One day, Akira gets lost in a world where wizards and humans coexist. In this world, the moon that attacks the world is feared as a "great disaster", and Akira, as a sage, saves the world together with the wizards who fight against the moon. Akira participates in a parade in the royal capital with the wizards and is welcomed by the townspeople. However, there is also a wizard who does not appear... 
 
The story of the battle between the wizards and the sage and the moon unfolds.
 
(Source: Natalie, translated)