Taisetsu wo Oshitsukerareta Seijo

Chelsea has a special ability to grow plants. One day, she was suddenly recognized as a saint who brings fertility to the country and was summoned to the castle. When she was unable to fully demonstrate her power, she was forced into the Aldamann family. Eventually, the castle's cold treatment of her would change completely and gain the affection of the marquis. Her brother-in-law Dainan immediately falls in love with Chelsea, and he can't stop loving her all the time! Miracles continue to occur one after another around them as the fantasy love story unfolds between a false saint and her brother-in-law. (Source: Libre, translated)