Tokyo - Japan's top court on Monday dismissed the appeal of an inmate sentenced to die for a 2008 stabbing rampage that killed seven people.
The Supreme Court decision comes four years after the original sentencing of Tomohiro Kato, now 32, who ploughed a rental truck into a crowd of shoppers in Tokyo's bustling Akihabara district before he stabbed passers-by.
The attack also left 10 people injured.
The presiding judge at Kato's sentencing in 2011 said the killing spree was "a brutal crime that did not show a shred of humanity on the part of the defendant", adding the death penalty was the only suitable punishment.
Japan is the only major industrialised democracy apart from the United States to impose the death penalty, usually for cases of multiple murder. It has more than 100 inmates on death row, where the condemned are executed by hanging.
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Kato's noon-time rampage shocked Japan, which has a low violent crime rate, and cast a spotlight on the online bullying that led up to the attacks in Akihabara, a centre for the manga comic and anime film subculture.
At one court hearing, Kato said he had committed the crime because he had been the target of online bullying.
"I wanted people to know that I seriously wanted to stop the harassment on the Internet bulletin board I was using," he was quoted as saying.
It was not clear when Kato would be executed.
International advocacy groups have denounced the Japanese system, under which death row inmates can wait for their executions for many years in solitary confinement and are only told of their impending death a few hours ahead of time.
However, the death penalty is widely supported by the Japanese public.