Hakuouki: The Last Old Blood.

Chizuru Yukimura was living peacefully with the Shinsengumi while looking for her father. Just then, a traveling individual named Sei had arrived in Edo looking for her. Sei was wandering around at night searching for her whereabouts when he met with some ronins along with the furies. Confused and surprised he might had been, he has thought to use this as a lead to find Chizuru, but became a reason with his encounter with the Shinsengumi to take him with them because of his connection with Kodo and Chizuru.

When the two met, it was the same time Kazama Chikage, another oni, "visited" the Shinsengumi. He was shocked when he found Sei with them. It was then revealed that Sei is a woman and is about 200 years old. She is an old blood oni, who was once became a guardian of Kazama's ancestor. Due to Kazama's respect to Sei and his ancestor, he didn't bother the Shinsengumi that night but warned them to protect both Chizuru and Sei as they might get entangled with the oni conflict.

Hakuouki: The Last Old Blood is a fanfiction written by Zhaie Yuemn. Any resemblance to real persons, living or dead, is purely coincidental or used in fictitious manner.