Their clothes, ostentatious jewellery and swagger mark them out as the "yakuza" gangsters who oversee the city's drug and sex trades, its protection rackets and extortion scams.
Yet more Japanese look at Samir with thinly veiled suspicion, even alarm, than at these underworld thugs.
Samir has dark hair and eyes as well as the aquiline features of his native Morocco. He has been granted permanent residency in Japan, has a full-time job and his daughter is half Japanese.
But still the assumption for some is that he is a terrorist.
"I used to have a beard and on one occasion a customer told me I looked like a terrorist," he said.
"If I were blond and had blue eyes, I wouldn't have any problems, but because my name is Samir and I have a beard, I'm a terrorist." He shaved the beard off shortly after the invasion of Iraq.
Passport to prejudice
Although born and raised in Morocco, Samir has dual nationality. "I always use my French passport," he says.
"If I used the Moroccan one, it would be terrible. I wouldn't be able to do anything. I've learned not to say that I'm Moroccan because that just causes problems."
Security on the Tokyo metro has
been stepped up
An estimated 200,000 Muslim immigrants presently live in Japan, as well as around 10,000 Japanese who have converted to the religion.
But their lives have become more complicated since the arrest of a group of eight men suspected of having links to an al-Qaida activist who lived in Japan.
The arrests are part of an ongoing police investigation into the activities of Lionel Dumont, 33, who was working as a used-car dealer in the city of Niigata between July 2002 and September 2003 while allegedly laundering al-Qaida money. Dumont was arrested in Germany in December.
"We know that he was in contact with people all across northern Japan, not just Niigata prefecture, but we don't know all their names or whether they are still here," said Tomio Koiwa, a spokesman for the prefectural police.
"The most important task now is to find them, and that is what we are trying to do," said Koiwa.
"We have increased security at stations and airports in the prefecture and we are calling on local residents to report to police any people who are acting unusually."
Japanese police have been acutely embarrassed by the revelations that Dumont, who is of Algerian descent, was living in Japan on a forged passport that identified him as Tinet Gerald Camille Armand.
And with Japan's Self-Defence Forces in Iraq and Tokyo offering wide-ranging support to the US government, there is concern at home that Japan itself might become a target.
Japan's involvement in Iraq has
led some to fear attacks
That fear has been reinforced by warnings, purportedly from al-Qaida, that the SDF would be a target "as soon as they set foot in Iraq" - but also that Japan could expect attacks at home.
"Attitudes among Japanese people towards Muslims have definitely changed," said Khalid Kimio Kiba, a Japanese who converted to Islam 40 years ago and who is presently director of finance at the Islamic Centre in Tokyo.
"All Japanese people's opinions of Muslims changed after the 11 September 2001 attacks in the United States and we are afraid," he said.
"We spend a lot of time telling people that we are a sincere group dedicated to peace, that we are neither al-Qaida nor the CIA, but we have to be very careful nowadays."
Every week, an officer from the Tokyo Metropolitan Police visits the Islamic Centre in the western suburb of Setagaya to ask questions in a "very nice" manner, he says.
And, working with immigration officials, police have introduced other checks, he says, particularly on individuals renewing visas, those involved in transferring large sums of money either abroad or within Japan, or anyone with a criminal record.
"I ask my Japanese friends whether they believe I have links to al-Qaida and even they say that they can't be 100% free of suspicion"
Khalid Kimio Kiba,
director of finance,
"Muslim people are very afraid because we have a bad image," said Kiba.
"I ask my Japanese friends whether they believe I have links to al-Qaida and even they say that they can't be 100% free of suspicion.
“They believe rationally that I'm not bad, but they say they can't be absolutely sure as long as I am a Muslim."
There are around 30 purpose-built mosques around Japan, as well as more than 200 temporary places of worship, according to Abd al-Rab Shaji, who helped found the Islamic Centre in 1974.
"We concentrate on preaching and the promotion of Islam," said Shaji, a Pakistani national.
The country has more than 30
"Our audience is Muslim expats and people who want to convert to Islam, but we are not involved in politics.
"At the moment, our biggest aim is to build a school for Muslims here and we are trying to find the finances for that project."
Other efforts are under way to get the message that Islam does not equate to terrorism across to the Japanese public. Idris No Madjid founded Ummah Media and began publishing Wawasan Kepulauan just days after the 11 September attacks.
"I did it to make people here understand, to give the other side of the story," says Madjid, who arrived in Japan from Indonesia 30 years ago.
"The news here is not balanced with Islamic news and people just don't understand Islam. It doesn't explain the details, but only shows violence and terror."
The 5000-circulation Japanese-language newspaper contains adverts for halal restaurants, airlines that fly to Muslim countries and a map of mosques and prayer rooms around Tokyo; editorially, it is aimed squarely at addressing the media imbalance.
And, while that may take some time to achieve, Madjid plans to do all he can to bridge the gap between two cultures and religions so that the suspicion and fear might one day be a thing of the past.