“It has been four years since the Battle of Sekigahara, which is said to have split the country in two. That was when the name Demon Eyes Kyo, the killer of a thousand men, became a legend. But Demon Eyes Kyo lived on… inside the traveling chemist, Mibu Kyoshiro. When Demon Eyes Kyo awoke from within Kyoshiro, an unknown chapter of history started to unfold.”
During such times, Yuya Shiina, a girl who earns money by collecting bounties, mistakes a traveling chemist, Mibu Kyoshiro, for the legendary outlaw "Demon-Eyes Kyo". Even though Yuya intends to turn him in, Kyoshiro defends her when a demon attacks. About to die, Kyoshiro mumbles, "Here he comes," and the color of his eyes turn a hellish red. He draws his untouched sword, and suddenly, Demon-Eyes Kyo, the legendary killer of a thousand men emerges to defeat the demon, saving Yuya and himself.
Kyoshiro and Kyo: Two souls trapped in one body. Yuya is looking for a "man with a cross-shaped scar on his back" who killed her older brother.