Onmyouji Abe no Seimei Series

Centering on the historical figure Abe no Seimei, one of Japan's most famous onmyōji (ancient Japanese occultist). The story begins when Abe no Seimei inadvertently assists Princess Tachibana during Kyoto's Kamosai festival, and finds out that she is possessed by a formidable spirit. Source: MU