SAITAMA – A week after the fatal stabbing of a female college student in Iruma, Saitama Prefecture, police are struggling to understand what drove the self-confessed knife man, described by acquaintances as a “nice young man,” to commit a brutal murder.
Shizuka Sato, 21, from Iruma, was walking home from her part-time job at a convenience store on the evening of Oct. 15. She was attacked from behind and stabbed so hard that in some places the knife’s handle entered her body.
She was found with more than 30 stab wounds in her back, chest and abdomen. Police suspect the killer used a combat knife.
Police arrested Yusuke Numata, 20, from Saitama last Thursday after he turned himself in, later telling investigators he had sought to target “someone vulnerable.”
Investigators have revealed no history of aggression by Numata — and no sign that he and the victim knew one another.
A member of staff at a fire station where Numata has served since January described the suspect as a gentle, kind and sincere person, adding that he was often willing to take initiative.
Investigators said the case “will take time” to unravel.
“During his junior high school years (Numata) played in the school’s soccer club and was elected class representative,” one investigating officer said. “We haven’t heard anything negative about him from his friends.”
But people who were in contact with Numata on a regular basis told the police they noticed a change in his behavior about a year ago.
Numata had enrolled in a class for aspiring police officers at Nihon Bunka University. He said he began to miss classes regularly in the middle of his first year there. He entered the second year but then took no tests or exams.
Investigators believe he had little attachment to the school.
“It’s not that I had a strong desire to become a police officer,” they quoted him as saying.
A person who claimed they were acquainted with both the victim and the suspect said that Sato had reported being followed by someone.
This raised suspicions that Numata had been stalking her. But police came to believe he knew the victim only nominally at best, and they discarded the idea that Numata and the victim were acquaintances.
Police also quoted Numata as saying he had felt frustrated and had wanted to “vent” his feelings.
“I bought the knife about a week ago,” he reportedly said. “I just wanted to kill anyone and so when I saw the woman leave the convenience store, I followed her.”
As Numata’s motive still remains unclear, an investigator said the investigation has drawn insufficient evidence regarding how Numata’s mental condition influenced his actions.
However, another senior investigative officer described Numata as someone who seems to have “developed a split personality, between the gentle side and the insane side.”