Crimefighters hunting accused English teacher killer Tatsuya Ichihashi may have received their biggest tip yet from a man who claims to have had sex with the fugitive twice in recent months, and even provided investigators with a pair of undies belonging to the wealthy doctors' scion for DNA testing, Josei Seven (5/1) says.

The 35-year-old man identified by the women’s magazine only as Mr. A, a Tokyo-based company employee, claims to have met the 29-year-old Ichihashi at what Japan’s gays call a "hattenba".

Hattenbas are cheap, dark places where men pay a small fee in return for a modicum of privacy while they engage in casual, usually anonymous sex with other guys who’ve come in looking for the same thing.

Mr. A says it was one such hattenba in Tokyo’s gay quarter of Shinjuku Ni-Chome where he came across Ichihashi during a steamy February encounter. His tale has provided one of the strongest of thousands of leads police have received since Ichihashi slipped through their grasp during a bungled arrest attempt after the body of British teacher Lindsay Ann Hawker was found in his apartment in March last year.

Mr. A says the man he met and made love to at a hattenba in February deliberately avoided showing his face, his attempts at hiding made easier by the dark lighting in the room where their alleged encounter was supposed to have occurred.

“Based on past experiences at hattenbas, I’ve never heard of someone trying to hide their face from a partner for the whole time. I thought he must really be scared about being seen. I thought it was a bit shifty,” Mr. A tells Josei Seven, noting that a flash of light gave him a glimpse of his partner's puss. "Right that instant, I thought to myself, 'I've seen that face somewhere.' I knew I could remember having seen him, but couldn't for the life of me remember where."

Mr. A tells the women's weekly about their meeting.

"We were at it for about 20 minutes and though he moaned and groaned, he didn't utter a single word. He came first, so I ejaculated inside him. I got up to go and have a shower, but he showed no sign of cleaning himself off, inside just hiding under the blankets on the bed in the room. Most people finish and go straight to the showers, so I thought to myself that he must be really scared about showing his face," the homosexual man says.

Ayumi Sakai, a writer specializing on Japan's homosexual culture, says the hattenba offer fugitives like Ichihashi a wonderful place to keep a low profile.

"Many hattenba operate 24 hours a day. You can get in by paying only a small entrance fee. They're nearly always dark, so as long as you're a man you can go in there for any length of time and stay hidden regardless of whether you're gay or straight," she tells Josei Seven. "If a young guy finds a willing partner outside of the place, he may find someone who'll pay for him to get in and stay there. Once you're inside, there's no need to say a word, even your name. They have showers, saunas and places to sleep. They're perfect places for criminals hiding out who don't want to be seen anywhere."

Chiba Prefectural Police, the force heading the hunt for Ichihashi, officially say the many rumors about Ichihashi's presence in the gay quarter have nothing to do with the real investigation into Hawker's murder. But others say it's a different matter and point to the large number of detectives seen in Shinjuku Ni-Chome since last summer.

Investigators sifting through Ichihashi's computer found that he had quite an interest in gay sex, and a search of his home revealed that he was also a cross-dresser, prompting police to add to their wanted poster an artist's impression of what the alleged killer might look like if done up as a woman.

Mr. A, for one, has no doubts about Ichihashi's preferences, saying a second encounter at a hattenba in March convinced him. Mr. A had left the facility and was outside talking to a friend when a man he was convinced had been the guy he'd just slept with walked out. Mr. A says his friend immediately noticed the other man's resemblance to Hawker's presumed killer, so he and the friend tried to take a photo of him with their mobile phones.

Lindsay Ann Hawker, captured on a security camera prior to her death.

"We thought that if the guy really was Ichihashi we had to catch him. He must have heard us say his name because when we reached the corner where he'd turned, he had suddenly run off and ducked into a little alleyway," Mr. A says. "I wondered whether I should go to the cops, but my friend said he wanted nothing to do with it. I lost my courage then and went home to have a good think about it."

Mr. A says he spent the night poring over the photos of Ichihashi that the Chiba Prefectural Police have put online.

"The more I looked at them, the more convinced I was that the guy from the hattenba was Ichihashi," Mr. A says. "Reporting the incident to the police was really hard because it meant exposing my sexuality. And I worried that it may not have been worth it if the guy was not actually Ichihashi. But I thought that if it was the real Ichihashi, I had no other option but to let the cops know."

Mr. A says he eventually told the police of his suspicions. They questioned him and he led homicide detectives to the place where he had the steamy encounter with the man he believes was Ichihashi. Though he held onto them at first, Mr. A says he also presented police with something that may help identify his mystery partner.

"Actually, I took home a pair of his undies after the first meeting," Mr. A tells Josei Seven. "It's not uncommon at a hattenba to take home a reminder of someone you've met up with there. But taking something without asking is a crime, so I was reluctant to let the police know. I wasn't happy with the police, either, because they kept asking me the same things over and over and over again and I stopped trusting them, wondering whether they were really serious about the investigation. I eventually gave them the undies, but I have my doubts about whether they'll actually do anything with them."

Chiba Prefectural Police say they are currently having the undies DNA tested to confirm whether they actually belonged to Ichihashi. Mr. A has his worries, though, saying that he had already washed them in the time from the meeting until he gave them to the police on April 8, but experts say that DNA can still be tracked down on items that have been through a washing machine.

Josei Seven (5/1)

Chiba Prefectural Police, meanwhile, say they're doing all they can to track down Ichihashi after he raced off barefoot and penniless when a cordon of officers had him in their clutches last March. Police say that 45,777 officers have served on the case and the public has generated 4,137 tip-offs.

"Police have formally asked for assistance from about 5,000 businesses in (Tokyo entertainment districts such as) Shinjuku, Shibuya and Ikebukuro. There have been plenty of cases in the past where tip-offs from ordinary people led to crimes being solved," a police insider tells Josei Seven. "Police have got to follow-up every single lead they get in this case if they want to solve it."