Takafumi Horie, former boss of Japanese internet firm Livedoor who quit amid a corporate scandal, has pleaded not guilty to fraud charges in court.
Mr Horie had become a friend of Japan's prime minister
Mr Horie denied violating securities laws by falsifying profit figures to boost Livedoor's share price.
The 33-year old faces a maximum of five years in jail if found guilty.
Mr Horie's fall from grace sent shockwaves through the Japanese stock market, leading to a sharp fall in share prices earlier this year.
The case against Mr Horie has attracted widespread public interest because his brash, aggressive manner was at odds with Japan's traditionally conservative business culture.
Mr Horie and other Livedoor executives were forced to resign in January after being accused of conspiring to massage Livedoor's profits to give the impression that the firm was continuing to grow strongly.
Four colleagues including the firm's chief financial officer have admitted their guilt but Mr Horie, whose case has taken much longer to come to court, has denied all charges.
In his first public appearance since being given bail in April, Mr Horie told a Tokyo court that he was "offended" by the allegations.
"I regret this indictment," he said. "I have never done such things and I didn't order such things either."
Mr Horie is accused of instructing his subordinates to artificially raise profit figures to maintain the internet's firm growth profile.
Prosecutors also claim Mr Horie used unscrupulous methods to buy other companies and to hide Livedoor's growing losses.
The case will hinge on whether prosecutors can prove that Mr Horie was aware of wrongdoing and conspired with other executives.
"The arguments of the prosecutors collapse on their own," defence lawyer Yasuyuki Takai told the court.
"The prosecutors are portraying acts that are totally not criminal as though they are great crimes."