Three people were stabbed outside the University of Tokyo on Saturday before an exam day, and police detained a student suspected of carrying out the attack.
The victims are an 18-year-old boy, a 17-year-old girl and a 72-year-old man, according to police.
The lives of the two young men are not in danger, but the older man was seriously injured, local press reported.
“We arrested a 17-year-old student for allegedly stabbing (the three victims) in the back with the intent to kill,” a Tokyo police spokesman told AFP.
The student was detained by police at the entrance of the prestigious University of Tokyo after the attack, it added.
He did not have to appear for the exams and did not know the victims, but he told the police, according to the public broadcaster NHK: “I wanted to die after causing an incident, since I did not do well in studies.”
NHK said the university center, where 3,700 students had to take the exams, continued with the planned tests.
Violent crime is rare in Japan, but there have been several knife attacks lately.
On October 31, in the middle of Halloween, a very popular holiday in Japan, the police arrested a 24-year-old man for attempted murder after the knife attack he perpetrated on a train, where he also caused a fire, causing 18 injuries. .