Born with a weak constitution, Hiromi desperately wished to conceive a child with Kurama, but their attempts failed to produce a child, even resulted in a miscarriage, and her health deteriorated from the effort. Their last resort was in-vitro fertilization , and this time, they were lucky. The resulting child was Mariko, but Mariko's DicloniusSilpelit nature, caused by Kurama's exposure to an escaping Diclonius child, was unknown to both her parents due to Hiromi believing it was more fun to wait and see the child's sex at birth instead of having an ultrasound scan during her pregnancy. During Mariko's birth, there was a complication wherein the doctors discovered Hiromi had cervical cancer, so her entire uterus had to be removed at the same time Mariko was delivered via Caesarean Section. The removal of her uterus would make Mariko her only child.
Hiromi dearly loved Mariko as soon as she saw her, but her husband was shocked and distressed at the sight of the newborn, knowing many Diclonius children are the primary cause of death for their families once their vectors develop at age three. Hiromi had no idea that his job, kept secret from her, was to euthanize infant Diclonii as soon as they were born. He immediately began to strangle Mariko, but Hiromi, shocked to see this and weakened by the surgery removed during birth stopped him before collapsing. When he tried again later, a tearful Hiromi, beset by massive internal bleeding, rose from her hospital bed to beg him to stop and make him promise to love their child and not kill her. She then collapsed and bled to death, dying in Kurama's arms as he begged her to wake up. After her death, Kurama held to his promise to Hiromi, albeit with mixed results. To those who would ask, he would respond about his family to say his family was dead, even going so far as to say he killed both his wife and his daughter. In his eyes, this was indeed the truth. Hiromi is later seen in visions Kurama has of her and Mariko walking into heaven together.
In the anime, Kurama sees visions of Hiromi just before he dies alongside Mariko, imagining a life with his wife and child they could have had if Mariko hadn't been born with horns.
Hiromi shares her voice actress with her daughter in the English dub: Luci Christian.
It seems unlikely that Nana ever knew Hiromi's name, but since she believed Kurama to be her father, she likely might have thought Hiromi was her mother as well. The two share many similarities, including their devotion to Kurama and a desire to bear his children.