Futa Monster Girl

When faced with the choice to remain as the sixth female in the line of succession for the throne of Harmonie, with all that entailed, or setting out on her own, Princess Neia didn't think twice before becoming an adventurer. Her father tried to dissuade her from what he called a fantasy, but when he saw there would be no convincing Neia, he ensured she would have the best protection available, and enough coin for her new life.
It had been more than a decade since, and the elf didn't regret her choice. She saved hundreds of people over the years, fighting all kinds of creatures and monster girls, putting her life on the line for what she felt was right. And then she came upon Tenelusia, where some locals hired her to deal with an attack by two monster girls. It didn't take her long to realize there was more to the story, because Tenelusia hid quite a dark secret, one that will fill Neia with horror.