Risa Kagami was the late wife of Shiranuma, now known as Byaku. Fearing that her husband would lose interest in her once her beauty faded, she became obsessed with achieving eternal beauty. This obsession ultimately led her to take her own life after becoming disfigured in one of Shiranuma's experiments.
The demon Kagami adopted Risa's surname and form as part of a contract with Heisuke Matsudo. Despite her marriage to Byaku, Heisuke harbored feelings for Risa. After her death, he used an Ayakashi to possess her body so she could serve as his assistant.
According to Byaku, Risa had an angelic face but was manipulative at heart. She skillfully controlled him, always getting what she wanted. Her requests for luxurious attire and jewelry continued even after marrying Shiranuma. In response, Shiranuma began conducting experiments on her to preserve her beauty and grant her immortality. Regardless of the outcome, she consistently encouraged him.
One fateful night, one of Shiranuma's experiments went terribly wrong, leaving Risa horribly disfigured. Shiranuma handed her a knife, left the room, and she stabbed herself in the heart. As per her request, he burned down their home and dug two graves, one for her and one for himself. He buried her but left his own grave empty.
Sometime later, Heisuke exhumed both graves. Finding Shiranuma's grave empty, he assumed that Byaku had taken Risa with him. However, upon uncovering Risa's grave, he discovered her corpse and was overcome with grief. He took her body to his laboratory, attempting everything possible to revive her, though he knew it was futile. Eventually, he gave up and summoned an Ayakashi, making a contract to create Kagami, who took on Risa's form and appearance.
In the final battle between Heisuke and Byaku, Heisuke asked if Byaku had ever truly loved Risa. Byaku admitted that he had never loved anyone in his life.
