Police served a further arrest warrant Sunday on a 16-year-old boy in Ibaraki Prefecture for allegedly killing a woman by repeatedly stabbing her.
The second-year senior high school student in Tsukuba, Ibaraki, whose name is being withheld because he is a minor, has admitted to killing 42-year-old Yasuko Shinji, saying he "just wanted to stab someone," according to the Ibaraki Prefectural Police.
He was arrested earlier this month for allegedly disposing of Shinji's body in a river in neighboring Ryugasaki on June 30.
The boy told investigative officials during interrogation about stabbing the victim from behind. He told the police he did not know Shinji, who lived in Ushiku, a city adjacent to both Tsukuba and Ryugasaki.
The boy turned himself in to the police on July 5 with his parents after a passer-by found the victim's body floating in the river earlier that day.
Police suspect the boy stabbed Shinji on a street in Tsukuba on June 30 before dumping her body.
The police believe a fish pick, a tool used by fishermen to keep dead fish fresh, was used to kill Shinji.
One was found near the river.