The ruling Liberal Democratic Party (LDP) was so scared of what might come out in Mr Kanemaru's trial that it deliberately scheduled the elections to be held last Sunday, four days before the trial, even though it meant pre-election campaigning clashed with the Tokyo G7 summit.
The court case will be followed with rapt attention in Nagatacho, Tokyo's political district, as the LDP, of which Mr Kanemaru, 78, was a prominent member, struggles to find a successor to the unpopular Prime Minister, Kiichi Miyazawa. Mr Miyazawa is expected to announce his resignation today, and there is a battle royal within the party over his successor. The last thing a potential prime minister wants is to be named in Mr Kanemaru's trial.
But, given Mr Kanemaru's former position as the godfather of the party, and his inside knowledge of the delicate art of political fundraising, he probably has enough information to put the entire party behind bars for many years if he were to 'squeal'. For years Mr Kanemaru was the head of the construction zoku - the group of politicians who represent the construction industry's interests in parliament, and are rewarded handsomely for doing so. Construction firms are known to pay more political bribes than any other industry, largely because of their reliance on big public works projects.
And if this all sounds more like a gangster thriller than a political story, then it will come as no surprise to know that Mr Kanemaru, a judo black belt, was known informally as 'The Don' during his political career.
There is a nice symmetry in the Kanemaru case. For many, Mr Kanemaru is the epitome of the system of money politics that had reduced Japan's democracy to a nationwide payola scheme, and his arrest last March for income tax evasion is regarded as poetic justice. Politicians campaigning for the elections last Sunday repeatedly said there must be reform of the old ways.
But Mr Kanemaru was the first man who thought of fundamentally reforming politics by setting up a real opposition party to the LDP - an idea that has now been realised by his erstwhile lieutenant, Ichiro Ozawa, in the form of the Shinsei (Renewal) party. The Shinsei party won 55 seats in the elections.
Mr Kanemaru's lawyers have made no comment on the trial, but reports say he will try to defend himself by claiming the money on which no tax was paid - and which was found in the form of cash, gold bars and anonymous bank debentures in his house and office - was intended as seed money for a new political party, and not for his personal use.
A number of commentators have suggested that the reason Mr Kanemaru is in court in the first place is that influential LDP politicians wanted to hijack the Don's plan to split the party and set up a new challenger for power, and so leaked damaging information to the public prosecutors. Politicians everywhere know how to fight dirty when their power base is threatened, and these days the threat to many Japanese politicians is particularly serious.