Yakushi to Maou: Towa no Kenren ni Saku

Seina Satou, who works as a pharmaceutical researcher, suddenly finds herself lost in a different world! One day, after managing to start life as the pharmacist 'Sena', she encounters a mysterious man. He is the demon king Dermatitidis, a man of immense beauty and strong magical powers, but sickly and weak. Sena's knowledge and experience in herbal medicine is recognized, and she becomes his personal apothecary, with whom he shares a special and unforgettable time. And so, before long, the two are drawn to each other.

(Source: MU)