But public prosecutors believe more than 100 politicians, including at least two serving cabinet ministers and three former prime ministers, received bribes from Sagawa that may add up to pounds 160m. At the same time, embarrassing stories of huge flows of funds to one of Japan's largest yakuza, or gangster, syndicates are emerging. The effect has been that of an air-raid siren on the political world, with LDP and opposition members desperately diving for cover.
Yesterday 17 cabinet members were questioned about their involvement with the Sagawa company when they attended a session of the House of Councillors' Audit Committee. Like schoolboys summoned before the headmaster to discover who had let the air out of the teachers' tyres, they all sheepishly denied having accepted any money from Sagawa. Many, however, seemed to be suffering from amnesia about their relations with the trucking firm.
Michio Watanabe, the Foreign Minister, admitted that the top executives of the Sagawa company were 'acquaintances', and said he might have received an invitation to one of their parties some time ago. Koichi Kato, the chief cabinet secretary, said: 'There were no donations, but I met Mr Sagawa last year - or maybe a year before that.'
If it were not for the amount of money involved, the Sagawa affair would be quite a comedy. But public prosecutors believe that, on top of the political 'donations', the trucking company was also involved in some pounds 2bn of shady loans, with possibly one-fifth going to fund yakuza enterprises.
But despite the seriousness of the allegations, the Japanese electorate has shown little anger or even surprise at the way their politicians seem to walk around with a permanent 'For Sale' sign on their backs.
So pervasive is Japan's system of money politics that businessmen, local councillors and a whole gamut of officials and special-interest groups are all enmeshed in mutually beneficial financial back-scratching. An ordinary politician would expect to spend pounds 500,000 a year on presents and other sweeteners for his constituents and supporters, a sum that could treble or quadruple for cabinet ministers.
And despite press reports that the Sagawa scandal is 'rocking' Japan's political world, in fact there is little likelihood that much will change, just as little changed after the Lockheed bribery scandal in the 1970s or the Recruit scandal in the 1980s. Many of those tainted in the Recruit scandal - after which the LDP vowed to purge itself of 'money politics' - are again suspected of taking money from Sagawa. The scramble for shelter is largely motivated by the fear of each politician of being left out in the open to take the rap for the rest who get away.
At the moment, the most likely candidate for symbolic fall-guy appears to be Mr Kaneko. The province is home to both the former prime minister, Kakuei Tanaka, who was at the centre of the Lockheed scandal, and Kiyoshi Sagawa, the founding chairman of the firm that bears his name. Mr Kaneko is now being questioned by prosecutors on suspicion of having received 300m yen ( pounds 1.2m) in illegal political donations.
The prosecutors want to charge Mr Kaneko with violating the Political Fund Control Law. If they do, he will be the first politician indicted under the law since 1954.