Mayumi Igarashi: The only civilian who knew Jiban's secret identity. She lost her memory in battle, after falling from a waterfall, because, Biolon put in her finger a Bomb Ring. If Jiban approaches her, the bomb will burst. She called Naoto her 'big brother,' only to find that she was really his lost sister in the finale. In the Filipino Dub, she is renamed as Kathleen.