Ms Nagai is an ordinary person living in an ordinary house in Nagaoka, a small town in Niigata prefecture. She has three children, and her mother and father also live in the house, as is the custom in the countryside. The main room has a television, and a sideboard where she keeps a golfing trophy won by her husband. It is still in its plastic bag to keep off the dust. There is a pot with plastic flowers and a painted Japanese doll. On the wall is a calendar from a construction company with views of Niigata.
'Yes, politically he was criticised,' she admitted. Mr Tanaka was arrested in 1976 for taking bribes from Lockheed and is widely regarded - and reviled by many - as the father of Japan's system of money politics. 'But we in Niigata still feel ninjo for him: he did so much for this area.'
Niigata never had it so good as when Mr Tanaka became prime minister in 1972. The formerly poor, isolated farming prefecture on the west coast was suddenly transformed into an enormous building site. Expressways were built, tunnels dug through mountains, new roads appeared everywhere and, most spectacularly, a branch line of the 'bullet' train was built from Tokyo to Niigata.
All were symbols of Mr Tanaka's largesse - and his control of the bureaucratic mechanisms in Tokyo for allotting public works projects. Never before or since has Japan seen a politician so adept at bending the system to his own will.
Ms Nagai was getting excited, though, because out of the blue Mr Tanaka's daughter, Makiko, 49, suddenly announced last month that she would run for parliament in the upcoming elections. It looked as though the 'Tanaka Legend' was going to be revived.
Mr Tanaka, now 75, has been written off many times but, as if in a Dracula film, he has refused to die. After being arrested in 1976 he resigned from the Liberal Democratic Party, but his mastery of money politics was so strong that his power actually increased, and he went on to appoint three prime ministers. In 1983 a court found him guilty of accepting bribes from Lockheed; Mr Tanaka filed an appeal and carried on regardless. Only when he had a stroke in 1985 which confined him to bed did he seem finally to have bowed out of the political scene.
But now his daughter is campaigning on his name, and he has recovered sufficiently to stay at his home in Tokyo and receive occasional guests. 'If he came down here and drove through the town and just waved his hand out of the car window, that alone would be worth 10,000 votes,' said Ms Nagai.
Makiko Tanaka may not even need her father's appearance to win a seat. The old Tanaka campaign support groups are being remobilised, and in every speech she makes she drops his name relentlessly.
Ms Tanaka says she is interested in clean, money-free politics and social welfare issues, caring for the handicapped, the oppressed and the sick - 'like my father'. But the Japanese are long accustomed to looking for the 'real intention' behind the 'surface appearance'. Makiko Tanaka, suggested Ms Nagai, is only getting involved to keep the Tanaka name alive for her son, Yuichiro, 23, who has just graduated from university. The intention, thinks Ms Nagai and many people around Niigata, is to forge a Tanaka dynasty. And what did the young Tanaka study? Commerce.