This woman, whose name was never revealed in the series, fell in love with Raizen and bore him a child. She and Raizen are Yusuke Urameshi's ancestors. She is voiced by Colleen Clinkenbeard in the FUNimation dub and by Mika Doi in the Japanese dub.
Raizen's lover had long dark hair, reddish purple eyes and pale skin. She wore a dark-blue kimono with an obi sash. Raizen describes her as "the most beautiful creature he had ever seen." She had rather large breasts, and possessed a very curvy, feminine figure.
While only her insides and blood are corrupted in the anime, in the manga Raizen sees that the rotting flesh she ate has taken its toll on her body, as her flesh seems to be rotting and corrupt as well, making it much more threatening in the manga.
She heals Raizen after he sustained injuries while on a raid in a Human village. After healing him, Raizen attempted to eat her in her sleep, but she was aware of his attempts. She taunted about his eating habits, and warned of the toxins and poisons in her body, that could even kill him, but gave him a choice to eat her or leave. Through this interaction, the two eventually fell in love with each other. Because of her, Raizen swore to never feed on humans again, and thus began to slowly starve to death over centuries.
She had a temper, but was also apparently very intelligent. Raizen says that Yusuke has demonstrated her fiery temper.
700 years ago, in her time, the human world was a very different place. The kekkai barrier had not yet been erected, and there was chaos and disorder throughout the land. The humans of the time were in constant fear as they lived side-by-side with demons, and the daimyō weren't above contracting their help in order to defend their territories from rivals and enemies. Raizen explained that at that time in his life, he was particularly uncaring because he saw all humans as food.
He then talked to Yusuke about how he couldn't find it in himself to care that in her eyes, he could see his downfall; he had fallen in love. He then goes on to talk about how she was a medicine woman and healer at the time, being an esoteric Buddhist doctor who practiced medicine by ingesting deadly poisons and contagions in order to turn her own blood into primitive vaccines. Her techniques were surprisingly effective, and his wounds healed quickly.
When the woman fell asleep, Raizen began thinking about how to eat her. The woman woke up and taunted Raizen, stating he may eat her, but that her flesh and blood turned toxic and polluted enough over the years in her tenure to kill him, and that he'd better hurry up with whatever he ended up doing. She then stripped naked to show Raizen that this was no bluff and to let him eat her. Raizen was mesmerized by her fearlessness, and the two of them ended up making love. The result of their sexual intercourse with each other resulted in conceiving their child.
In the morning, however, Raizen left after realizing that he wasn't worthy of her. His reasoning was that she had devoted her life to saving people, while his life had been nothing but destruction, and vowed to never eat another human being until he saw her again. After he left, Raizen's lover spent the remaining time carrying Raizen's child in her womb that he impregnated with. Unfortunately, he was never to see her again, as she died in childbirth.
The night they consummated with each other resulted in conceiving a baby who was mixed with demon blood from Raizen and human blood from his lover. Raizen, however, left after their child's conception. After finally giving birth to the child, the woman died of childbirth. Raizen's child was able to live long enough to have his/her own child, and thus started a family line of humans with demon ancestry, who were descended from Raizen. Yusuke was born from these humans 44 generations later, making him a direct descendant of Raizen. Raizen spent years searching for her reincarnation, but ultimately realized that she was far too enlightened to be brought back to this world. Before his death, he stated that he hoped to be reunited with her in the next life. It was stated that Yusuke inherited most of his personality and temper from her.