Along with a 26-year-old Hokkaido University student who was investigated over an allegation that he was planning to join the Islamist extremist militant group Islamic State, a second man in Tokyo had also planned to travel with him to Syria, according to senior officials of the Metropolitan Police Department.
In addition to the two men, several other people had made inquiries after seeing an advertisement recruiting people with an interest in travelling to Syria, the MPD's Public Security Bureau said.
The MPD bureau aims to question the men and other interested parties to examine how and why they planned travel to Syria.
The Hokkaido University student was investigated by the MPD on suspicion that he attempted to join the Islamic State as a foreign fighter.
According to MPD officials, the man in Tokyo lived in a house in Suginami Ward, Tokyo, where the Hokkaido University student also lived after coming to Tokyo. He was in contact with Ko Nakata, a 54-year-old former university professor, with the intention of making a travel plan.
Nakata is a researcher of Islam and gave advice to the Hokkaido University student about how to travel to Syria.
A third man, in his 30s, related to a secondhand bookstore in Chiyoda Ward, Tokyo, where the advertisement had been displayed, also lived together with the two in the same house.
The advertisement invited people to "work in Syria."
According to the MPD, several men visited the house. A woman who was acquainted with the Hokkaido University student and some related individuals said: "Various types of people came to the house.
They included those who were interested in military affairs and others discontented with society."
The Hokkaido University student was in contact with Nakata via the man related to the secondhand bookstore and initially planned to depart for Syria on August 11, but the trip was cancelled just before his intended departure.
Another man, a part-time worker in Chiba Prefecture, also planned to go to Syria with the student. But he gave up on the plan because of opposition from family members.
The man in Tokyo planned a rescheduled departure for Syria with the student on October 7. Kosuke Tsuneoka, a 45-year-old journalist, also planned to travel with the Hokkaido University student from this date.
The several others who had made inquiries about travelling to Syria cancelled their plans before details of the arrangements were decided, according to the MPD.
Regarding Syria, where armed conflicts are ongoing, the Foreign Ministry issued an advisory to evacuate from the country.
It is the most serious overseas travel advisory that can be issued by the ministry within its four-stage alert structure for countries presenting risk.
The MPD Public Security Bureau has also raised alerts about the fact that several young Japanese attempted to go to Syria.
Regarding the situation, Osamu Miyata, head of the Center for Contemporary Islamic Studies in Japan, said, "In the United States and European countries, too, there have been many cases where young people, feeling discontent with their societies, have been attracted by extremist ideas and then joined the Islamic State."
"But don't they understand the possibility that they may kill civilians and children on the battlefield? It's irresponsible that they participate in a war to fulfil their personal desire," he said.