Police officers stormed into the rail carriage and took the man into custody after the train, carrying some 880 passengers, made an emergency stop at Odawara station.
In police questioning, Kojima admitted carrying out the assault, saying that he did it because he was feeling frustrated and that he randomly attacked people on the train, according to the sources.
The suspect, identified as Ichiro Kojima, attacked the victims around 10:00 pm local time (1300 GMT) aboard the shinkansen train which was travelling from Tokyo to a station in Osaka, Kyodo News reported.
Police said two female passengers in their 20s were injured, though their conditions were not life-threatening.
One of the injured women told the police Umeda had tried to stop the attacker when he began wielding a knife at her. "We would like to be left alone for now". Another knife was found on the train.
Witnesses spoke of 20 to 30 passengers panicking and fleeing from the direction of the No. 12 auto.
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Witnesses said passengers were in tears as they attempted to flee in panic.
Kojima left home in Okazaki in Aichi Prefecture, central Japan, last December, according to an 81-year-old woman believed to be a relative of the suspect.
After being hospitalized for an undisclosed mental illness, he started working for a machinery maintenance firm in April 2015 but quit in February the following year.
The incident reportedly occured aboard a Shinkansen bullet train running near Tokyo.
According to the Kanagawa prefectural police and other sources, three passengers on the train were attacked.