Tokyo 23 wards are very dense and compact, feel somewhere like Paris. Outside the 23 wards, 180 degree is surrounded by the mountains or sea leading to Saitama's radish fields and Chiba's deserted coastal rural villages. Even the outer wards for instance Setagaya and Suginami are very countryside. I don't think therefore Tokyo being the world's largest city. The sprawl is in fact very small. Even if Kanto has some 45 million people, I reckon the Tokyo's urbanised area itself is acutally tiny, consist of some 5 million people or so.