Mahiru Saginomiya (鷺ノ宮まひる Saginomiya Mahiru) was a girl that appeared in Ultraseven X 100 years ago prior to the series.
A hundred years ago, Saku and his younger brother, Nozomu stopped at the Saginomiya household to seek a temporary refuge, after having journeyed through various places on Earth. Nozomu eventually fell in love with Mahiru and vice versa but unfortunately, everyone around her protested their relationship and their marriage plans. Nonetheless, Nozomu swore that he would always stay by her side. After Mahiru realised that Nozomu was afraid of water, she determined to know how much Nozomu loved her and asked him to get the water lily from her household pond. Unfortunately, this became her undoing as it transformed him into Jyuujin who then killed her before he ran away into the underground tunnels and slumbered for a hundred years.
Her action would lead Jyuujin into becoming a murderous killer whom hunted down women with Mahiru's appearance/white dress without accepting the fact that he had killed Mahiru. After being detected by DEUS agents, The monster's rampage would finally end when Jin/Ultraseven X killed him via his Eye Slugger.
- Mahiru was similar to Asami Agata from previous the episode of Ultraseven X as both of their deaths were by their loved ones going mad and transforming into monsters while later denying the truth of their lover's death.