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Appearance and Personality
She is physically weak despite her age. Her weakness started being apparent in her mid-teens, but from the age of 20, she was confined to a motorized wheelchair. Even with the slightest of bodily exertion she becomes exhausted. Her appetite is small which means that she doesn't get enough nourishment, which makes her body weak in a vicious circle. Her undeveloped figure is a result of that. It is noted by Mayumi that there is a very slight bulge in Mio's chest area that can be seen while she is clothed, so calling her completely "flat" wouldn't be much of an exaggeration. Her hip area is also as thin as a young girl. Mio’s body looks like it belongs to someone around the age of thirteen. 
Mio is 26 years old as of AD 2095 in November. 
Her brother, Itsuwa Hirofumi, and she herself live together at one of the Itsuwa Family residency's in Tokyo since he started attending University there after she graduated. He also takes care of her. 
Her being a Strategic-Class Magician makes her one of the Thirteen Apostles and is what affords the Itsuwa Family their position among the Ten Master Clans. Her Strategic-Class Magic is Abyss, which is the trump card of the National Defense Force. 
- A type of Movement Systematic Magic that has its own classification, Fluid Control. The magic can create a spherical depression in water with a diameter up to several kilometers and a depth of up to a kilometer. Ships caught in the zone would slide down the walls of the water, then upon cancellation of the magic, would be swallowed up by the massive waves as the water returned to a horizontal plane. The depth of the sphere allows for the destruction of submarines as well.
- It can also be used on subterranean ground-water, allowing it to destroy any structures on top of it. This magic is theoretically capable of destroying fleets with a single usage, earning it its classification as a Strategic-Class Magic.
- It is unknown exactly whether or not Mio attended the Magic University or not.