Misato Mikami is the younger sister of Shiro Takamachi and biological mother of Miyuki Takamachi. After a terrorist organization bearing a clover-leaf symbol killed their extended family, Misato entrusted Miyuki to Shiro's care and departed to pursue vengeance against those responsible. This led to Miyuki being raised as Shiro's adoptive daughter alongside his biological children, including Nanoha Takamachi, making Misato Nanoha's maternal aunt.

Her absence during subsequent events resulted from her commitment to an anti-terrorist force in Hong Kong. There, she trained her nephew Kyouya Takamachi and daughter Miyuki in sword combat, passing down the inherited Mikami-ryuu sword style. Kyouya later mastered both Mikami-ryuu and Fuwa-ryuu. Misato's legacy influenced Kyouya and Miyuki's dedication to protecting others, particularly their childhood friend Fiasse Crystela.

Within the Reflection manga continuity, Misato appears in a cameo alongside Shiro and his children during a conversation between Momoko Takamachi and Lindy Harlaown concerning Nanoha's future.