Elf no Futago-hime: Willan to Arsura

There's a world where humans and elves live together. Elves rule the world because of the intelligence and longevity. But one day, humans surge in rebellion plus a big war breaks out. From a long battle, both countries choose to prevent the war by the marriage of convenience. Arsura, a princess of elf country, is chosen as a bride. However, when jane is to be with her approach to a person's territory, she and Willan, her sister and guard, are kidnapped by someone! While elves and humans push responsibility to one another, several monsters appear! It's them who kidnapped elf sisters. Their boss is Darsh, that's half human and half elf. What exactly is his purpose...? Another war breaks out now!