Mr Kanemaru, 78, was the real power behind Kiichi Miyazawa, the Prime Minister. He has long been regarded as the political godfather of the ruling LDP, and is nicknamed 'the Don'.
The scandal over the Sagawa Kyubin delivery firm has been simmering for months since police arrested two of the company's executives in February. The two men were suspected of involvement in some Y500bn of shady loans to other companies and Y40bn of donations to leading political figures in Tokyo.
More than 100 politicians are thought to have received money in exchange for political favours from the trucking firm, which also had links with Japan's yakuza, or gangster syndicates.
By his resignation yesterday, Mr Kanemaru may be trying to load all the blame for the scandal on his shoulders in the hope that his LDP colleagues will get off free.
In a televised press conference, Mr Kanemaru said: 'I have to apologise to all the members of the LDP. I feel I should take responsibility. I deserve to resign for receiving the money.'
The Y500m was paid to Mr Kanemaru in the run-up to the general elections in 1990, when the LDP was still reeling from the last big political scandal in Japan revolving around the Recruit company, and badly needed money to boost its chances in the elections.
But despite his confession yesterday, Mr Kanemaru could not bring himself totally to repudiate the system of money politics of which he was a master and which has kept the LDP in power since 1955.
'Although (receiving money) is against political ethics, my feelings to appreciate the favour haven't changed at all,' he said defiantly.
The question which is now hanging over the LDP is whether Mr Kanemaru's resignation will be sufficient to head off the Sagawa scandal, or whether it
will start a witch hunt for other
senior politicians involved, as happened in the Recruit affair in 1988-89.
A whole string of politicians, including Mr Miyazawa, who was then finance minister, and Noboru Takeshita, then prime minister, were forced to step down for having accepted shares in return for favours from Recruit.
As politicians tainted in the Recruit affair quickly rehabilitated themselves, the Sagawa scandal is unlikely to have any lasting impact on Japanese politics.