Midori Niwano (庭野 ミドリ), also known as Ms. Midori (ミドリ先生), is an elementary school teacher in Metro City. She is 27 years old and is very supportive of Astro and other robots with kokoro. Her Japanese voice actor is Sanae Kobayashi, and her English voice actor is Faith Salie.
Ms. Midori is smart and hard-working young teacher, and is protective of her students. She is modern and very open-minded. She is also very pro-AI, and gladly welcomed Astro into her class as her first ever robot student.
When Midori was a child, she was chosen to thank the giant robot Jumbo at the first annual Robot Expo. Jumbo responded so kindly that it gave her a life-long love of robots, and she considered Jumbo a family friend ever since. She has two parents who are still alive, and it is implied she had a very normal and positive childhood.
In the present, Midori lives alone in her own apartment, which overlooks the Metro City bay where Jumbo sits.
Ms. Midori primarily teaches 4th and 5th grade, and is dedicated to her role as a teacher. She cares very much about her students. She has even volunteered to chaperone them on extracurricular outings throughout Metro City. She often uses state-of-the-art technology in her lessons, such as immersing her class through interactive hologram programs. Other students in her class include Tamao, Kenichi, and Shibugaki.