The Saint's Magic Power is Omnipotent (Manga) Vol. 5 von Yuka Tachibana

With her workaholic life on Earth further and further behind her, Sei is truly coming into her own as the living Saint of the kingdom of Salutania. Experimenting with her unique holy magic, she finds new ways to fortify both herbs and potions with strength never before seen. It's a strength she may soon need to rely on, because the day is drawing close when she'll join the royal knights on their campaign to subjugate the wild monsters of the land. When the kingdom marches on a monster-haunted forest, it'll take all the powers of a Saint to make sure everyone comes home safe!