Miwa is Machi's younger sister. She is first introduced as a schoolgirl with a strong personality who occasionally assists Machi and Amamiya in their investigations. As the series unfolds, her significance grows as more details about her involvement in the overarching conspiracy are unveiled.
It is later revealed that she is a new generation bar-coder, carrying a critical alternate personality essential for the creation of Lucy Monostone. Her final significant role appears to be transferring Kazuhiko Amamiya's personality to Nishizono Tetora.
