Takayama, 65, who heads the Nagoya-based Kodo-kai gang affiliated with the Yamaguchi-gumi, was given the sentence by a three-judge panel at the Kyoto District Court.
He had pleaded not guilty and denied he had any intention of extorting the 67-year-old businessman.
Takayama, in conspiracy with other Yamaguchi-gumi gangsters, was charged with carrying out the extortion in 2005-2006.
During the trial, the victim testified that Takayama had forced him to work under the influence of the gang. Presiding Judge Akihiro Ogura, in handing down the decision, said the victim's testimony was reliable.
Prosecutors had sought 10 years in prison for the defendant, saying that Takayama persistently demanded that the businessman pay him money.
Among the conspirators was Yoshiyuki Takayama, 56, who heads the Omi-Ikka gang also affiliated with the Yamaguchi-gumi and based in Otsu, capital of Shiga Prefecture. Yoshiyuki Takayama is also charged with extortion and his trial is under way.
The Yamaguchi-gumi is based in Kobe, Hyogo Prefecture. The number of its member gangsters was about 31,000, about 44 percent of the country's gangster population of 70,300, as of the end of 2011, according to police data.
Kiyoshi Takayama: The No 2 man in Japan's biggest crime syndicate, the Yamaguchi-gumi, was sentenced to six years in prison on Friday for having extorted 40 million yen (USD 420,000) from a construction business operator.
First Published: Friday, March 22, 2013, 15:58