Yakushi to Maou: Eien no Kenren ni Saku

A medical researcher named Sena Satou ends up in a different world, where she begins a new life as a medicine-man called "Sena." She meets Delmatitidis, a demon lord with striking appearance and powerful magic, though he is physically frail and ill. He acknowledges her expertise in herbal medicine and hires her as his personal apothecary. Over time, they grow close and develop a strong connection. Their relationship evolves into a romance that alters the course of their lives.