Teito no Oni wa Sakura wo Kou

Since ancient times, Japan has been home to beautiful demons with supernatural powers. When Otoha, a budding onmyoji, was a child, her mother was killed by a young red-haired demon, and she lost all memory of what happened before that. Otoha vows to repay the kindness of Tsukikage Touma, the head of the Onmyo Bureau, who took her in and raised her after she had lost her family, and to take revenge on the demons. One day, while pursuing a woman who resembled a demon, Otoha meets the beautiful demon leader, Homura. Otoha braces herself for her mother's enemy, but for some reason, Homura treats her sweetly and gently...

(Source: Kadokawa, translated)