Ni-kai no Youkai Oujo

is a Japanese light novel series written by Ryuji Arai, with illustrations by Kantaka. The series began publication on May 10, 2005 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
"You inherited the mansion left by your distant ancestors." Yukito, a lonely high school student who came to a town near Tokyo, was guided by a sudden letter. However, in the old samurai residence, the Hyakki clan, a youkai who longs for Yukito's ancestor Onmyoji as a benefactor, settled in. The beautiful girl, Youhime, who unites the Hyakuki clan, unilaterally recognizes the upset Yukito as the main, and begins living together with the clan party. Yukito keeps being swayed by youkai who are good but out of common sense. Meanwhile, at that time, the evil youkai sealed by Yukito's ancestors are also released. The comedy series opens.