Boroboro no Elf-san wo Shiawase ni Suru Kusuriuri-san

An apothecary lives a quiet life selling potions and medicine in a country village, until one day he's approached with a devil's bargain. A pawnbroker offers him the perfect ingredient for crafting legendary medicine—but the "ingredient" turns out to be a mortally wounded elf! Legend has it the flesh and bones of elves can be ground up into a true panacea, and this elven maiden is on the brink of death after being ruthlessly tortured by slavers. Filled with rage, the apothecary vows to nurse her back to health and happiness, no matter what it takes.

(Source: Seven Seas Entertainment)

Adapting the light novelization of the web comic of the same name.