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“Maru” of “Marunouchi” means circle (〇) in Japanese, “Otemachi” also has a circle (〇) as an initial letter in it’s name.
OAZO, is a name that express “Office & Amenity Zone (=AZ),” between these two (O) areas comprehensively.
Furthermore, “OAZO” means “oasis” in Esperanto.