| Region | Population | Area in km2 | Prefectures contained |
| Hokkaidō | 5.1 million | 83,000 | Hokkaidō |
| Tōhoku | 8.9 million | 67,000 | Akita, Aomori, Fukushima, Iwate, Miyagi, Yamagata |
| Kantō | 43.3 million | 32,000 | Chiba, Gunma, Ibaraki, Kanagawa, Saitama, Tochigi, Tōkyō |
| Chūbu | 21.4 million | 67,000 | Aichi, Fukui, Gifu, Ishikawa, Nagano, Niigata, Shizuoka, Toyama, Yamanashi |
| Kansai | 22.5 million | 33,000 | Hyōgo, Kyōto, Mie, Nara, Ōsaka, Shiga, Wakayama |
| Chūgoku | 7.3 million | 32,000 | Hiroshima, Okayama, Shimane, Tottori, Yamaguchi |
| Shikoku | 3.8 million | 19,000 | Ehime, Kagawa, Kōchi, Tokushima |
| Kyūshū & Okinawa | 14.3 million | 44,000 | Fukuoka, Kagoshima, Kumamoto, Miyazaki, Nagasaki, Ōita, Okinawa, Saga |
| Region | Prefectures |
| – | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| – | Tokyo |
| Kantō | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Kanagawa, Niigata, Nagano, Yamanashi, Shizuoka |
| Chūbu | Toyama, Ishikawa, Fukui, Gifu, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| Region | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Kantō-Kōshin'etsu | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Nagano, Niigata, Yamanashi |
| Tōkai-Hokuriku | Toyama, Ishikawa, Fukui, Shizuoka, Gifu, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| Region | Prefectures |
| – | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Kantō | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Yamanashi, Nagano |
| Hokuriku | Niigata, Toyama, Ishikawa |
| Chūbu | Nagano, Gifu, Shizuoka, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama, Fukui |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima |
| – | Okinawa |
| Region | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Kantō-Kōshin | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Yamanashi, Nagano |
| Hokuriku | Niigata, Toyama, Ishikawa, Fukui |
| Tōkai | Gifu, Shizuoka, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Northern Kyūshū | Yamaguchi, Fukuoka, Saga, Nagasaki, Kumamoto, Ōita |
| Southern Kyūshū-Amami | Miyazaki, Kagoshima |
| Okinawa | Okinawa |
| Constituency | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Northern Kantō | Ibaraki, Tochigi, Gunma, Saitama |
| Tokyo | Tokyo |
| Southern Kantō | Chiba, Kanagawa, Yamanashi |
| Hokuriku-Shin'etsu | Niigata, Nagano, Toyama, Ishikawa, Fukui |
| Tōkai | Gifu, Shizuoka, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| High court | Prefectures |
| Sapporo | Hokkaidō |
| Sendai | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Tokyo | Tokyo, Ibaraki, Tochigi, Gunma, Saitama, Chiba, Kanagawa, Niigata, Yamanashi, Nagano, Shizuoka |
| Nagoya | Aichi, Mie, Gifu, Ishikawa, Fukui, Toyama |
| Osaka | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Hiroshima | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Takamatsu | Tokushima, Kagawa, Ehime, Kōchi |
| Fukuoka | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| Region | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Kantō | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Kanagawa, Yamanashi |
| Tokyo | Tokyo |
| Tōkai | Gifu, Shizuoka, Aichi, Mie |
| Hoku-Shin'etsu | Niigata, Nagano, Toyama, Ishikawa, Fukui |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| Region | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | North: Aomori, Iwate, Akita South: Miyagi, Yamagata, Fukushima |
| Kantō | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Yamanashi |
| Tōkai | Gifu, Shizuoka, Aichi, Mie |
| Hoku-Shin'etsu | Niigata, Toyama, Ishikawa, Fukui, Nagano |
| Kansai | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |
| Region | Prefectures |
| Hokkaidō | Hokkaidō |
| Tōhoku | Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima |
| Hokuriku | Toyama, Ishikawa, Fukui |
| Kantō-Kōshin'etsu | Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Niigata, Yamanashi, Nagano |
| Tōkai | Gifu, Shizuoka, Aichi, Mie |
| Kinki | Shiga, Kyoto, Osaka, Hyōgo, Nara, Wakayama |
| Chūgoku | Tottori, Shimane, Okayama, Hiroshima, Yamaguchi |
| Shikoku | Tokushima, Kagawa, Ehime, Kōchi |
| Kyūshū-Okinawa | Fukuoka, Saga, Nagasaki, Kumamoto, Ōita, Miyazaki, Kagoshima, Okinawa |