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

Ichiro Kojima began planning the June 9 attack three months earlier and has shown no remorse over the "atrocious crime," 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 the death penalty.