The suspect in Sunday's attack lived alone and had a temporary job at a car factory, media said. He was reported to be a regular visitor to Akihabara, known for high tech electronic products sold alongside "anime" cartoon goods and cafes where waitresses dress as French maids.
FEELING LIKE FAILURES
Japan's obsession with exam grades made many feel like failures and the decline of the extended family had also cut support for troubled youngsters, said Jinsuke Kageyama, a criminal psychologist at Tokyo Institute of Technology.
"Japan has entered a period of selfishness. People have the feeling that they can do anything," he said.
"But when these people fail to fulfil themselves in socially acceptable ways, they are treated as losers and their frustration builds up," he added.
"A series of disappointments can lead them to try to regain their sense of self through crime."
Tackling the root causes of such attacks would be a complex task, and harsher penalties would likely not be helpful, he said.
Total reported crime has been falling for five years, but Japan has toughened up sentencing and increased the pace at which it carries out executions in recent months under Justice Minister Kunio Hatoyama, a supporter of the death penalty.
"If they have the urge to commit suicide, people will do these things in countries that have the death penalty," Kageyama said.
Some members of the public pointed to an economic downturn and government policy as reasons for rising frustration.
"Politicians don't think about the people, they raise taxes and change the healthcare system," said Kentaro Inoue, a 56-year-old worker for an architectural firm.
"I think that's what breeds this violent behaviour. People begin to hate society when they can't succeed."
Japan's top government spokesman, Nobutaka Machimura said it was hard to pin down the reason for Sunday's attack but tighter controls should be considered on survival knives like the one the attacker used.
