Midori Azuma is the mother of Tetsuya Azuma and wife of scientist Dr. Kotaro Azuma. Captured by the Android Army led by Buraiking Boss during his rebellion, her biometric data was transferred into Swanee (Suwanī), Buraiking Boss's swan-shaped robot pet. This transfer preserved her consciousness within the machine. From within Swanee, Midori covertly observed Buraiking Boss and gathered intelligence on the Android Army. When exposed to moonlight, Swanee projected Midori's hologram before her son, now the cybernetic warrior Casshern, providing strategic information and emotional support in his battles. As Swanee, Midori functioned as an undetected informant within the Android Army for most of the conflict.

Her holographic guidance relayed enemy plans, vulnerabilities, and critical updates to Casshern, proving instrumental in countering the Android Army's operations. Despite her synthetic form, Midori maintained her maternal connection, offering encouragement while acknowledging Casshern's internal conflict over his irreversible transformation.

Following Dr. Azuma's development of the Sprazer weapon, which annihilated most of the Android Army, Midori was restored to her original human body. She reunited with Casshern in his cybernetic form at the conflict's end, though his inability to return to humanity remained unresolved.

In the 2004 live-action film adaptation, Midori's portrayal diverges: she suffers deteriorating eyesight, motivating Dr. Azuma's Neo Cell research. After learning of their son Tetsuya's death in combat, she experiences visions of his ghost. Abducted by Neo-Sapiens during a laboratory escape, she is later recovered. The film concludes with Dr. Azuma attempting to resurrect her using Neo Cell technology, an act Casshern intervenes to prevent.