Allegations of fraud in a huge investment company and the bizarre bayonet murder of its chairman as 30 reporters stood by without intervening have stunned people across Japan, where safe streets and duty to society are considered national trademarks.

Millions of Japanese stared at television sets in disbelief last night as an incredible clip of news tape was aired repeatedly. It showed two men breaking into an apartment of Kazuo Nagano, head of the Toyota Shoji company, then emerging minutes later splattered with blood to boast that they had killed him.

"The city has become a wilderness without law," said a front-page commentary today in the mass-circulation Asahi Shimbun newspaper. The story dominated television and newspaper coverage all over Japan.

The slaying followed a weeks-old investigation of the Osaka-based company, which authorities believe took in about $800 million in funds during the past four years, much of it the savings of elderly people, and lost unknown sums in a variety of fradulent investments.

The Japanese lap up media stories about violent crime, although few have any direct experience with it. Statistically, their country ranks among the safest places on earth. Americans are more than 100 times more likely to be robbed than are Japanese and more than six times more likely to be murdered.

Still, this crime seemed sobering for many people here. It was another black eye for their vaunted police force, which for the past year has been playing an unsuccessful and highly publicized cat-and-mouse game with a gang that is trying to extort money from food companies by poisoning or threatening to poison their products on store shelves.

Some critics saw the affair as another sign of the emergence of an affluent but directionless society in Japan. "Crime is no longer committed to secure money or food to survive," said commentator Yukio Akatsuka. "More and more, it is due to sickness in the mind and heart."

Troubling, too, were the affair's implications for Japan's view of itself as one great extended family. The killing grew from what appears to have been a cynical and protracted scheme to misuse the savings of unsuspecting citizens.

And when Nagano, 32, was slain, 30 media people at the scene took no firm action to intervene.

Newspapers were swamped with calls today protesting the reporters' behavior. The Mainichi Shimbun newspaper reported this morning that one caller, a primary-school teacher, said: "My child was watching the TV and said, 'Why didn't they stop it?' What can I answer if I am asked that question at school tomorrow?"

Reporters on the scene later said that things had happened too quickly for them to have had a chance to stop the murder.

The case began unfolding several weeks ago, with press reports suggesting that Toyota Shoji (it has no links to the Toyota Motor Corp.) was in trouble. Established in 1981, the company expanded rapidly by selling the "Pure Gold Family Contract," which was said to represent an investment in bullion.

Armies of salespeople using high-pressure tactics canvassed the country. The gold would not be delivered, investors were told, but would stay in company hands and earn interest. Eventually, about 30,000 persons reportedly signed up, paying in about $800 million. Many were old people seeking high yields for their limited funds.

Company chairman Nagano founded close to 100 affiliated companies to channel the money, investigators believe. These delved into such diverse businesses as diamond trading, real estate, seaside resorts and commodity trading.

But some investors began complaining that Toyota Shoji was refusing to refund their contracts. The authorities began investigating and earlier this month closed several company offices and froze assets. No gold could be found. Officials now believe much of the money was lost in speculative schemes.

In the Diet, or national legislature, the government of Prime Minister Yasuhiro Nakasone came under fire for being slow in looking into the company, which officials say pioneered its type of gold contract in Japan.

Nagano was questioned by police on Monday in a tiny apartment he maintained in a low-rent district in Osaka, Japan's second-largest city. Reporters waited outside it, hoping for a statement from him on what was unfolding as one of the country's biggest financial scandals in years.

Yesterday afternoon, about 30 of them were crowded into the corridor outside its door when two men, later identified as Atsuo Iida and Masakazu Yano, pushed their way through. They harangued a security guard at the door, saying he should refuse his present work. "I've been told by six persons, 'We don't need money, so kill him,' " Iida was heard telling the guard.

The guard withdrew. The two men began tapping on the door and then smashing in panes of glass. With television cameras rolling, they climbed through a window. Muffled thumps and screams were heard from within. Photographers put cameras to the windows and snapped pictures.

The actual stabbing appears to have taken place outside of the reporter's field of vision. Reporters then saw the men pull the bloodied body of the victim close to a window. "This is Nagano," Iida said. "We did it." They then climbed out of the window, blood on their clothes. Yana carried a gory bayonet. Iida said: "I am the criminal. Call the police." Police arrived quickly and arrested them.

Motives for the slaying remain unclear.