Manga by author Yamada Fuutarou

Vow of Vengeance. Seventeenth-century Japan: A rebellion in the Aizu teritory has been brutally crushed, leaving twenty one brave warriors dead and most of the nuns of the local convent slaughtered. Now the surviving nuns have sworn to seek revenge. They turn to the greatest swordsman of the land to train them so they can kill the ones who slew the men and the other nuns.

By the order of Shogun Ieyasu Tokugawa, ten ninja from the Iga and the Kouga clans must fight to the death in order to determine who will be the next Tokugawa Shogun, with the surviving clan ruling for the next thousand years. But Oboro of the Iga clan and Gennosuke of the Kouga clan have fallen deeply in love. Now these star-crossed lovers have been pitted against each other. Can their romance conquer a centuries-old rivalry? Or is their love destined to end in death?