Gikeiki: Onmyouji Hougen no Musume

Kurou Yoshitsune secretly travels to Kyoto from Hiraizumi in Oshu to receive the legendary art of war from Oniichi Hougan. He was meant to receive the power from Hougan's daughter, Minazuru, who possesses the demon's art of war within her, but the spell fails. Yoshitsune disappears deep within Minazuru's body. Minazuru then heads to Hiraizumi as Yoshitsune, but...!? This historical fantasy follows the girl who has become Yoshitsune and the men who protect her! (Source: Akita Shoten, translated)