Greg Kelly, a former aide to ex-Nissan chief Carlos Ghosn, pleaded not guilty on Tuesday to a charge of financial misconduct as the trial against him began in Tokyo.
That has left Kelly the only person facing trial in the lengthy, rollercoaster saga involving Ghosn.
Kelly entered a plea of not guilty Tuesday to the single charge he faces -- conspiring to under-report tens of millions of dollars in pay that Ghosn was allegedly promised after his retirement.
"I deny the allegations. I was not involved in a criminal conspiracy," Kelly said.
He has consistently denied any wrongdoing, arguing -- as does Ghosn -- that no final agreement had been made on any post-retirement pay and therefore no disclosure was legally required.
Kelly, who turned 64 on Tuesday, entered the court dressed in a dark suit and red tie and wearing a surgical mask. He declined to speak to media gathered outside for the trial.
Ghosn's arrest in the Japanese capital in November 2018 on financial misconduct charges made headlines worldwide and kicked off an astonishing fall from grace for a man once hailed as a corporate saviour for rescuing Nissan from the brink of bankruptcy.
But overshadowed by his detention was the arrest that same day of Kelly, who has been out on bail in Tokyo since late December 2018.
The trial, expected to last around 10 months, centres around one question fraught with technicalities: did Kelly and Nissan between 2010 and 2018 illegally conceal payments of around 9.2 billion yen ($87 million at today's rates) promised to Ghosn on retirement?
Nissan, which is on trial alongside Kelly, says yes, and pleaded guilty to the charge against it on Tuesday.
But Kelly, who faces up to 10 years in prison if convicted, has insisted on his innocence since day one.
"I didn't do anything wrong," he told AFP in an interview in early September.
"Carlos Ghosn never got paid anything and he wasn't promised anything," he insisted.
Nissan and Japanese prosecutors disagree, arguing they have evidence that these future payments were pledged to Ghosn, and therefore should have been disclosed in the firm's financial filings as required by Japanese law.
Prosecutors have amassed a vast trove of documents, only a small portion of which the defence have been given so far, according to Kelly's lawyers.
Despite that, his team agreed to move to trial, arguing they had "no choice", with Kelly prevented from leaving the country and separated from his family while he waits for his case to go to court.
Kelly's legal team say they are confident he can be acquitted -- despite the track record of Japan's prosecutors, who win over 99 percent of the criminal cases they bring to court.
But they argue they have been put at a strong disadvantage by the court's refusal to allow overseas witnesses to testify by videoconference.
Despite the obstacles, Kelly's Japanese lawyer Yoichi Kitamura said he is "confident we can win the case".
Nissan has been tight-lipped about the trial, with a source close to the firm's leadership saying there was concern about negative media attention.
One of the trial's key witnesses will be Hari Nada, Kelly's former colleague, who obtained whistleblower status from prosecutors in exchange for his cooperation.
Former CEO Hiroto Saikawa, who was forced out over financial improprieties discovered by an internal investigation in the wake of the Ghosn scandal, will also give testimony.
The fact that he was able to resign without facing prosecution has been cited by Ghosn as evidence of what he claims is a biased justice system.
The former auto chief has defended his decision to flee Japan by claiming he would not have received a fair trial.