Seieki Kajiya no Eroranta

In a world where the Demon King threatens the peace, Kurt is a young man plying his trade as a blacksmith. He aims to become a full-fledged blacksmith, but for some reason, the only swords he can make are blunt pieces of junk. Elsa, the half-elf who works with him, always makes fun of him, but undeterred, he works hard every day at the forge. One night, while he's masturbating alone, lost in a fantasy, Elsa catches him in the act! By chance, the two of them discover that if his semen is squirted onto a dull sword, it becomes exceptionally sharp. And then Alesia, a female swordswoman who's a little, you know, catches wind of it and draws near.