The Saint's Magic Power is Omnipotent (Manga) Vol. 7

Summoned to another world at the end of a brutally long workday, Sei was shocked to find herself thrust into the role of savior. Yet there's no denying the holy power of her magic, or that it has helped protect the realm from darkness. Now she's been sent off to the Klausner Domain, a region known for its peerless accomplishments in alchemy and potion-making. There, a certain book falls into Sei's hands, one which contains the formulas for secret potions known nowhere else. Yet it's not what's written in the book that shocks her most, but the identity of its creator...!