At least 16 people have been injured in the mass attack and at least two people are reportedly dead. Police have confirmed one girl has died.
The suspect reportedly stabbed himself in the neck and was later detained. He has now died from his injuries.
The motive for the attack is unknown.
Police responding to the violent incident recovered two knives, said NHK.
A spokesman for the Kawasaki Fire Department told AFP news agency that an emergency call was received at 07:44 local time on Tuesday (22:44 GMT Monday) stating that a number of schoolchildren had been stabbed.
"I saw a man lying near a bus stop bleeding," a male eyewitness told NHK. "I also saw elementary schoolchildren lying on the ground... It's a quiet neighbourhood, it's scary to see this kind of thing happen."
The man reportedly started attacking people near a bus stop, not far from a local train station, according to reports.
Footage broadcast on local news stations showed emergency services arriving at the scene and setting up medical tents to treat the wounded.
Japan has one of the world's lowest rates of violent crime but in recent years has experienced a handful of attacks involving knives.
In 2016, 19 people at a care centre for people with mental disabilities were stabbed by a former worker. He reportedly said he wanted those with disabilities to "disappear".
Seven people were also killed during an incident in 2008 after a man drove a truck into a packed shopping district in Tokyo, before climbing out and randomly stabbing people.