Heian Oni-hime Souko

is a Japanese light novel series written by Kuroko Obana, with illustrations by Yomi Sarachi. The series began publication on October 10, 2010 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
The capital of Kyoto where a "mystery" called "princess killing" occurs. While the rare onmyoji, Seimei Abe, is searching for the cause, a young and immature onmyoji boy, Suzujo Sakagami, invites a boy, Genyori, who belongs to Sakonoefu, and begins his own "mystery" investigation.

Behind the reckless actions of the two, there was a desire to clear the suspicion of Suzujo's sister, Yuka, a girl who inherits the blood of demons. As expected, "love" woven by youkai and humans is deeply involved in "mystery" and "princess killing" .... A sad Yin-Yang Kitan is here.