On Sunday, Tomohiro, 25, was subdued after stabbing bystanders near the bustling train station of Akihabara, an area known for electronics stores that is a haven for fans of video-games and comic-book culture.
Earlier he had rammed a rented truck into a crowd of afternoon shoppers before getting out and stabbing people.
'Tired of life'
According to Japan's NHK broadcaster, the suspect said he was "tired of life".
Investigators examining the scene
of Sunday's crime [Reuters]
Stabbing attacks in Japan, once rare, have become more frequent in recent years, along with an increase in violent crime.
In March, a man with two knives stabbed one person to death and injured at least seven others outside a shopping centre in eastern Japan.
In one of the worst attacks in the country, a man with a history of mental illness burst into an elementary school in 2001, killing eight children with a kitchen knife.
The killer was executed in 2004.