The Saitama District Court sentenced a gangster to death Thursday for gunning down five other gangsters in December 2003.
Kaiichi Yamamoto, 58, the boss of a gang affiliated with Sumiyoshi-kai, killed 69-year-old Genichi Hosoda, the boss of another Sumiyoshi-kai-affiliate, and four other mobsters while the six were meeting in Iruma, Saitama Prefecture, according to the court.
Presiding Judge Shinichiro Fukuzaki called the defendants actions "persistent, cruel and antisocial."
"It is a heinous case rarely seen in criminal history," the judge said. "The containment of violence through violence cannot be condoned."
Yamamoto was on bad terms with Hosoda, who was ranked higher than him in Sumiyoshi-kai, and had heard rumors that Hosoda was planning to kill him or his relatives. Acting on this suspicion, he decided to murder Hosoda first, the court said.
Kokusui-kai gets made
The Tokyo-based underworld syndicate Kokusui-kai has become an affiliate of Yamaguchi-gumi, Japan's largest crime syndicate, according to police sources.
Police believe the move is part of Yamaguchi-gumi's nationwide expansion efforts. The Metropolitan Police Department said Kokusui-kai has about 470 members.