Shinichi's mother underwent experimental procedures conducted by her husband, Dr. Genzou Kuruma. He utilized bio-engineered cells containing undisclosed DNA during these tests, intended to advance his research into creating enhanced "New Humans." These experiments directly caused her death.
Her death formed a foundational trauma for Shinichi, profoundly shaping his motivations and emotional state. It established his core drive for vengeance against Genzou, whom Shinichi held responsible. After her physical death, her soul, alongside those of Maria Tengai and Ayaka Sanders, lingered within Shinichi's consciousness. These spirits collectively acted as a stabilizing presence, tempering Shinichi's rage and helping him control his transformative abilities and the destructive potential of his beast-like powers.
During the climax conflict with the artificially created God entity, this spiritual connection was severed when the entity violently expelled the souls of Shinichi's mother, Maria, and Ayaka from his mind. Their removal eliminated their calming influence, triggering Shinichi's catastrophic transformation into an uncontrollable giant monster driven solely by primal rage and grief. Her legacy remains intrinsically tied to both Shinichi's initial quest for revenge and his subsequent psychological and physical instability following the loss of her spiritual presence.