Yasuyuki Kitano and Harumi Sakamoto, both in their 40s, invited hundreds of guests, including Japanese celebrities, to a wedding reception in 2003, saying that Kitano was a member of a defunct branch of the imperial family.

Guests at Japanese weddings traditionally bring with them gifts of at least 30,000 yen (US$260) in cash.

Pictures shown on television at the time showed Sakamoto in the "junihitoe" 12-layered kimono worn by women of the imperial household on formal occasions.

"It was a malicious crime that cleverly took advantage of a mentality for revering the imperial court and imperial family," Kyodo news agency quoted judge Takaaki Oshima as saying.

Kitano and Sakamoto were both sentenced to two years and two months in jail.

Kitano said during the trial that he had been given the right to use the Arisugawa name, while Sakamoto said she believed he was a member of the royal family, Kyodo said.

The Arisugawa branch of the royal household died out for lack of a male heir more than 90 years ago, Kyodo said.