The Saint's Magic Power Is Omnipotent: The Other Saint (Manga) Vol. 3 (manga)

A normal afternoon trip to the convenience store turned into an otherworldly journey when Aira Misono was summoned to the Kingdom of Salutania. The handsome prince Kyle believed Aira to be the long-awaited Holy Saint--but as it turns out, an entirely different girl was the true savior. Aira now follows the path of a magician, and has become a valued member of the Royal Magi Assembly. While the Saint carries the weight of the world on her shoulders, Aira uses her powers to try and help carry just a little bit of that burden. Her latest plan is to try and create a purifying holy water to purge the monsters and miasma that threaten her new home!