From KManga:
This is not history as we know it. The year is 1600. Ten years have passed since Oda Nobunaga unified the whole of Japan. When Nobunaga realizes he is nearing the end of his life, he announces that he will hand over the reins of power to whoever brings him the strongest warrior. The generals, whose dreams of conquering the country had been crushed, put up their own strongest warriors and aim to become the king of the country! The first match is peerless spear wielder Honda Tadakatsu (sponsored by Tokugawa Ieyasu) vs. evolving prodigy Miyamoto Musashi (sponsored by Chosokabe Motochika).