Was looking through various historical election data and found that in 4- the member Lower House 群馬(Gunma) 3rd district in the elections
1963 1967 1969 1972 1976 1979 1980 1983 1986
The 3 LDP candidates and winners of all of them were
福田赳夫(Fukuda Takeo) - PM 1976-1978
中曽根康弘(Nakasone Yasuhiro) PM 1982-1987
小渕恵三(Obuchi Keizō) PM 1998-2000
The Lower House 群馬(Gunma) 3rd district which is Southern 群馬(Gunma) was clearly the district of PMs.
The 5th district appears to be its successor and could have produced another PM in Yuko Obuchi. However, she resigned from her ministry after a political funds misuse scandal.
https://www.reuters.com/article/japan-politics-princess/japans-obuchi-political-princess-could-be-first-female-pm-idINL3N0RV1B220141002https://www.reuters.com/article/japan-politics-resignation/in-blow-to-abe-japan-trade-minister-to-resign-over-funds-scandal-media-idINKCN0I62B720141018
