The geographical distribution of today's family names, moving roughly north to south from Hokkaido to Okinawa and listing the five most commonly found in each prefecture in order of occurrence.
Hokkaido: Sato, Takahashi, Sasaki, Suzuki, Ito
Aomori: Kudo, Sato, Sasaki, Kimura, Narita
Iwate: Sato, Sasaki, Takahashi, Chiba, Kikuchi
Miyagi: Sato, Takahashi, Suzuki, Sasaki, Abe
Akita: Sato, Takahashi, Sasaki, Ito, Suzuki
Yamagata: Sato, Takahashi, Suzuki, Saito, Ito
Fukushima: Sato, Suzuki, Watanabe, Saito, Endo
Ibaraki: Suzuki, Sato, Kobayashi, Watanabe, Takahashi
Tochigi: Suzuki, Watanabe, Saito, Sato, Kobayashi
Gunma: Takahashi, Kobayashi, Sato, Arai, Saito
Saitama: Suzuki, Takahashi, Sato, Kobayashi, Saito
Chiba: Suzuki, Takahashi, Sato, Watanabe, Ito
Tokyo: Suzuki, Sato, Takahashi, Tanaka, Kobayashi
Kanagawa: Suzuki, Sato, Takahashi, Watanabe, Kobayashi
Niigata: Sato, Watanabe, Kobayashi, Takahashi, Suzuki
Toyama: Yamamoto, Hayashi, Yoshida, Nakamura, Yamada
Ishikawa: Yamamoto, Nakamura, Tanaka, Yoshida, Yamada
Fukui: Tanaka, Yamamoto, Yoshida, Yamada, Kobayashi
Yamanashi: Watanabe, Kobayashi, Mochizuki, Shimizu, Fukuzawa
Nagano: Kobayashi, Tanaka, Nakamura, Maruyama, Ito
Gifu: Kato, Ito, Yamada, Hayashi, Watanabe
Shizuoka: Suzuki, Watanabe, Yamamoto, Mochizuki, Sugiyama
Aichi: Suzuki, Kato, Ito, Yamada, Kondo
Mie: Ito, Yamada, Nakamura, Tanaka, Suzuki
Shiga: Tanaka, Yamamoto, Nakamura, Nishimura, Yamada
Kyoto: Tanaka, Yamamoto, Nakamura, Inoue, Yoshida
Osaka: Tanaka, Yamamoto, Nakamura, Yoshida, Matsumoto
Hyogo: Tanaka, Yamamoto, Inoue, Matsumoto, Fujiwara
Nara: Yamamoto, Tanaka, Yoshida, Nakamura, Matsumoto
Wakayama: Yamamoto, Tanaka, Nakamura, Matsumoto, Maeda
Tottori: Tanaka, Yamamoto, Yamane, Matsumoto, Maeda
Shimane: Tanaka, Yamamoto, Sasaki, Fujiwara, Takahashi
Okayama: Yamamoto, Miyake, Fujiwara, Sato, Tanaa
Hiroshima: Yamamoto, Tanaka, Fujii, Sato, Takahashi
Yamaguchi: Yamamoto, Tanaka, Nakamura, Fujii, Harada
Tokushima: Sato, Yoshida, Kondo, Mori, Tanaka
Kagawa: Onishi, Tanaka, Yamashita, Takahashi, Yamamoto
Ehime: Takahashi, Murakami, Yamamoto, Ochi, Watanabe
Kochi: Yamamoto, Yamazaki, Komatsu, Hamada, Takahashi
Fukuoka: Tanaka, Nakamura, Inoue, Koga, Yamamoto
Saga: Yamaguchi, Tanaka, Koga, Matsuo, Nakajima
Nagasaki: Yamaguchi, Tanaka, Nakamura, Matsuo, Matsumoto
Kumamoto: Tanaka, Nakamura, Matsumoto, Murakami, Sakamoto
Oita: Sato, Goto, Watanabe, Ono, Kawano
Miyazaki: Kuroki, Kai, Kawano, Hidaka, Sato
Kagoshima: Nakamura, Yamashita, Tanaka, Maeda, Higashi
Okinawa: Higa, Kinjo, Oshiro, Miyagi, Aragaki
Source for both lists: "Myoji no Himitsu" ("Secrets of Family Names"), by Hiroshi Morioka (Asahi Shimbun Shuppan, 2009)