Mayumi is Mahiro's sister and was married to Muramasa for a period of time after he escaped from the Mibu clan. Mayumi's dead body been found by Mahiro, Kyo was beside Mayumi, holding a bloody sword in hand, which made Mahiro believe that he was the killer. She was killed four years ago by Chinmei in manga and Genza in anime. However, Mahiro doesn't find out the truth until much later in the story.