Mitsuko Komyoji, daughter of robotics scientist Dr. Komyoji and older sister to Masaru, grows into a protective guardian after her mother—a spy for antagonist Dr. Gill—abandons the family post-Masaru’s birth. Left to fill the maternal void amid her father’s obsessive lab work, her youth is defined by instability and emotional neglect, worsened by her mother’s eventual suicide following a brief reunion.

Her resentment toward robots, rooted in their role fracturing her family, softens upon meeting Jiro, a humanoid android crafted by her father. Discovering a disk implicating her father in Jiro’s creation, she initially blames the android for her father’s disappearance. Yet as Jiro aids her in unraveling her parents’ past, her feelings grow conflicted, wavering between distrust and cautious affection. Their bond frays under Dr. Gill’s manipulations, including a mind-controlling flute that triggers Jiro’s violent episodes.

Mitsuko’s journey navigates ethical tensions over artificial life, confronting Jiro’s duality as both programmed machine and morally conscious entity. She challenges societal prejudices to accept him, spurred by her quest to find her mother, who divulges intel on Dr. Gill’s headquarters before suicide. Mitsuko later joins battles against Gill’s regime, her resolve tested by loss and betrayal.

In later events, she clings to hope for Jiro’s return after his disappearance in a final clash, their relationship lingering in ambiguity. Expanded media alludes to her enduring belief in his humanity amid his existential struggles, though specifics remain unexplored.