Prosecutors requested a court on Monday to sentence a 23-year-old man to life in prison over a random knife attack aboard a shinkansen bullet train last year that left one person dead and two others injured.

Ichiro Kojima began planning the June 9, 2018 attack three months earlier and has shown no remorse over the "atrocious crime," the prosecutors said in their closing argument at the Odawara branch of the Yokohama District Court.

Kojima has admitted to the charges of murder and attempted murder, saying he tried to limit the number of fatalities to no more than two as he thought killing three people would result in a death penalty.

He has also said he wanted to spend the rest of his life in prison and is "not at all" sorry for the victims and their families.

Kojima underwent a psychiatric examination over a four-month period before prosecutors ruled him fit to face a criminal trial and indicted him in November last year.

However, they opted against seeking the death penalty based on a personality disorder.

Kojima killed 38-year-old Kotaro Umeda from Amagasaki, Hyogo Prefecture, by slashing him with a machete and a knife and seriously wounded two women in their 20s on the Nozomi 265 train en route from Tokyo to Shin-Osaka on the evening of June 9 last year.

Umeda, who tried to intervene Kojima's attack against the two women, sustained 78 wounds to his body, according to the prosecutors.

One of the injured women shared her feelings with the court during Monday's session.

"I feel so sorry for (Umeda's) family that I cannot really say I am glad to be alive," she said.

"Since the incident, I cannot go outside on my own, the shinkansen has become transportation I can never take again, and I am no longer able to go traveling," she said, adding she feels like she has died once.

Prior to the attack, Kojima had been homeless and sleeping outdoors, including in a park in Nagano Prefecture, according to the prosecutors.

Following the incident, shinkansen operators have made available shields and stab vests to police and other security personnel. They also increased the number of security cameras to allow for more stringent monitoring at stations and on trains.

The ruling is set to be given on Dec. 18.

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