Classes at Prince Hisahito's junior high school in Tokyo resumed Monday, with the 12-year-old prince attending as usual, following an incident late last month during which an intruder left knives on his desk.
Ochanomizu University Junior High School suspended classes last week in the wake of the April 26 knife incident, which occurred just before the start of the extended 10-day holiday from April 27 to celebrate the enthronement of the prince's uncle, then Crown Prince Naruhito, as the new emperor.
The prince did not appear to be nervous about going back to school, according to an Imperial Household Agency official.
Two knives attached to a stick with duct tape were found on the prince's desk at the school.
Police later arrested Kaoru Hasegawa for allegedly trespassing on the school's grounds masquerading as a contractor.
The school held a parents' meeting after the incident and apologized for not taking enough security precautions, pledging to strengthen measures to ensure the safety of students, according to people who attended the meeting.
Hasegawa is said to have told investigators he is against the imperial system and intended to stab the prince.
The imperial succession on May 1 promoted Prince Hisahito to second in line to the Chrysanthemum Throne.