Mahara Miko ~Okiyome wa Aiyoku Inbi ni~

The protagonist is Masato Mishiba, an ordinary high-school student who becomes possessed by a demon. By a rather convenient coincidence, the miko of the Kusakabe family have been pursuing the demon for quite a long time, and one of them happens to be his childhood friend Hiyori. Will Masato accept Hiyori's love, or will the demon inside lead him to increasing levels of depravity?

[from Eldwulf's review on DLsite English]