Kyou kara Akujo ni narimasu! Tsukaisute no Migawari Seijo Nante Gomen desu今日から悪女になります! 使い捨ての身代わり聖女なんてごめんです; Starting today, I'm going to be a villain! I'm not going to be a disposable substitute saint!

Princess Leonora is the one and only saint of healing. Ada, the maid of honor, who has been secretly healing people with her miraculous powers, has become a wreck due to the excessive use of her powers. Furthermore, Leonora, whom she had looked up to like a sister, has been cut down and thrown into the water! She thought she was already dead, she is rescued by a group of mercenaries from a big country and invited to become a real saint and show them how it's done!