Izumi Takashima is the deceased grandmother of Kei and Sui, as well as Midori's mother, Izumi appears to have been a gentle and understanding woman well loved by her family. She died from a serious illness when Midori was still a teenager and her death is the reason why Midori's relationship with her father is strained. When Kaname left her to attend a meeting at her request, her condition took a turn for the worse and died by the time he returned.

However, instead of asking for her husband in her final moments, Izumi asked for her steward, Kuze and Kaname believed she hated him for leaving her. Midori blamed her father for her mother's death and continued to resent him for never visiting her mother's grave, unaware that her father had tried many times, but felt too ashamed to do so. Years later, Kei manages to convince his grandfather to visit Izumi's grave in Australia, where it is revealed that Izumi's final request had been for Kuze to plant the flowers that Kaname would give her whenever he apologized over her grave. Upon seeing this gesture, Kei's grandfather is able to accept Hikari and Kei's relationship.