The suspect in the attack, who was arrested on the scene, says she randomly chose and stabbed a 53-year-old mother and her 19-year-old daughter. The victims' serious injuries are expected to take about three months to heal.
A restaurant worker near the scene of the crime told NHK that after the attacker was pinned to the ground, she stared up at the sky and asked if the daughter -- who sustained a 10-centimeter-deep wound to her back -- was dead. She didn't appear to put up any resistance, the witness said.
The Metropolitan Police Department found three small knives on the suspect, including the one used in the attack.
Junior high school suspect
The attacker has been identified as a third-year junior high school student from Toda in Saitama Prefecture.
She left her home around noon on Saturday, telling her family she was going to cram school. She reportedly took a train to Shinjuku Station, then walked to Shibuya Ward.
It was raining on the evening of the attack, and she chose an uncrowded alley near the bustling nightlife area. A security camera about 50 meters from the crime scene captured her walking about two meters behind the two women before attacking them. She told the police that she had been "looking for a quiet place to kill somebody."
The girl said she carried out the attack because she wanted to receive the death penalty. She also told police that she wanted to see "if people really die from stab wounds." Her ultimate plan was to kill her own family.
A spate of random attacks
The attack occurred just over a month after a 32-year-old woman stabbed a 13-year-old boy at a commercial facility in Fukuoka City. She, too, had chosen her victim at random and later told police that she picked a child because she thought it would guarantee that she would be executed.
In January, a man was arrested for holding a manager hostage at a Tokyo restaurant and claiming he had planted a bomb there. The suspect told investigators that he wanted to end his life by getting the death penalty.
Last October, a man dressed as the Joker from the Batman series stabbed more than a dozen people on a train in Tokyo on Halloween. The suspect told police that he thought his wish to receive the death penalty would be fulfilled if he killed more than two people.
Professor Harada Takayuki, a criminal psychologist at Tsukuba University, told NHK back in June that these attackers are motivated mainly by "an overwhelming sense of desperation about their own lives, and a desire to end them."
"With the spread of social networking services, they may compare their circumstances with those of others, become dissatisfied and turn against society, blaming those around them for their grievances."