Namaiki Dark Elf 3 Shimai ga Boku ni Nakadashi o Motomeru.

Oberu, an illegitimate son between a dark elf father and a human mother, is being treated like a lowly servant by his very own family. However he is fine enough and feels privileged being able to live in a fancy household together with his beautiful but disdainful elder sisters.
One day the oracle reveals that the child that will be born between Oberu and the woman he'll love will rise on top of all dark elves and bring glory for a thousand years. Unwilling to pass such opportunity to other aristocratic families, their father orders that he must marry one of his very own elder sisters.