Close to tears, Issei Sagawa bemoans the fact that notoriety doesn't pay nearly as well as it used to. He sips a strawberry milkshake on the terrace of a cafe in a suburb west of Tokyo and tells me that he can see no reason to continue living, that he has no friends or money any more, that he is ill and being harassed by the police. He says he constantly thinks about killing himself, "but I'm too scared to actually do it".

"I just wish it was all over," he says, looking down mournfully.

Physically deformed - Sagawa, 64, is under five feet tall, has a head that is too large for his body and stumpy fingers on child-like hands - he also suffers from diabetes and it would be easy for anyone unaware of his dark past to feel some sympathy for this curious-looking but extremely intelligent fellow.

On stepping into his cramped and chaotic apartment, one begins to get a better feel for the man. And for the monster that lurks within that seemingly innocuous little body - the monster that convinced Sagawa, as a student at the Sorbonne in Paris in 1981, to shoot 25-year-old Dutch student Renee Hartvelt in the head, to sexually abuse her corpse and then to carve her up and eat parts of her body.

I first met Sagawa a decade ago. Back then, he hinted that he was a bit short of cash and I paid for the coffees, but the last 10 years have clearly not been kind to him. Where he was once dapper, he is now down at heel. The suit is shiny at the elbows and the shoes are scuffed. His mobile phone has only just been reactivated after he scraped together enough cash to pay an outstanding bill.

But it is in his face that the change is most visible. Sagawa used to at least take care of his unusual appearance; today, greying whiskers have been missed with the shaver, his cheeks are hollower and his movements are more nervous, more sudden.

However, although circumstances have forced him to exchange a roomy, bright apartment in Chiba for a dingy property in industrial Kawasaki, some things have not changed. There is no name on the plate by the front door - Sagawa says his neighbours do not know who he is and he wants to keep it that way - and stepping into his kitchen-cum-dining room is an assault on the senses.

Plastic flowers, a gaudy blue Mexican sombrero, a poster from a Pushkin exhibition and pictures cut crudely from pornographic magazines adorn the walls, the sides of cupboards and the refrigerator. Overdue bills lie on the table alongside a framed still from the porn film he starred in after his return to Japan (in the shot he is pretending to consume an actress' buttocks) and a plastic rose in a vase.

Sagawa's bedroom is separated from the rest of the apartment by a pink curtain and contains an orthopaedic bed and seven remote control handsets on a bedside table. A cabinet contains dolls, porcelain figurines, hand towels featuring the seven dwarfs from Snow White and a candelabra. The surround of the flat-screen television has been decorated with cut-out images of girls in bikinis and provocative poses. A traditional scroll hangs on the wall and fluffy toys - a bear, an owl, a puppy - sit along the bed, beside a copy of Charles Baudelaire's Les Fleurs du Mal.

Above the washing machine, in an alcove by the toilet, is a colour print of Sagawa and a woman both baring their buttocks on top of a hill.

Another room serves as his study and is different from the rest of the apartment in as much as it contains no images of naked women. Here there are formal, black-and-white portraits of his parents, who died on consecutive days in January 2004, and photos of Sagawa and his brother as boys playing in Kamakura, where they grew up. A large Leni Riefenstahl poster covers most of the sliding door of the closet, juxtaposed with fliers from exhibitions by Monet, Edgar Degas and Ilya Repin. There are bookshelves and an easel, a heavy armchair, a desk, but no computer; Sagawa says he cannot afford one. Instead, he writes longhand on squared paper.

If his working space is sanitised and respectable, under the stern gaze of his deceased parents, Sagawa's tiny bathroom is the opposite. More explicit images have been cut from magazines and carefully placed on the walls behind a layer of protective plastic sheeting. Other pictures are of foreign women befriended by Sagawa but who fled after learning of his horrific past.

He met them in hostess bars when he was flush with cash from publishers and television stations, bought them dinners and dresses, paid for holidays and won their confidence. These trusting young women - convinced that Japan was the safest nation in the world - saw Sagawa as a slightly odd but harmless and wealthy patron. The advent of the internet and the ability to discover people's dark secrets with a few clicks of a mouse changed all that.

"I have no friends any more," he says. "I feel there is no reason for me to do anything. I do not know why I am here. I can't write any more as no one wants to publish my books any more; I can't paint because my eyesight is so weak."

Wallowing in self-pity, he comes back to his thoughts of suicide.

"I think about killing myself every day, but I haven't been able to bring myself to do it yet."

Then, suddenly, he switches to a sense of outrage over what he claims was botched treatment at a local hospital earlier this year, an episode that led to his arrest.

"I nearly died," he says. "There was something wrong with my chest, my throat and my heart and I ended up with blood in my lungs. I'm a diabetic and they gave me too much medicine and it affected my brain."

Released after three weeks of treatment, he returned to a neighbourhood in which he lived eight years ago, walked into someone's garden and started measuring paving stones.

"I knew what I was doing, but I didn't know why I was there or what I wanted to do."

Arrested and questioned by police - "they treated me terribly" - he claims it was only the intervention of the duty doctor that enabled him to cheat death for a second time in a matter of weeks.

After a further two weeks in hospital, he returned to his home, his collection of indecent images and his efforts to make enough money to scrape through another month.

While we have been talking, we have been tiptoeing around the shocking crime for which Sagawa hit the headlines. It was a crime he effectively evaded punishment for and which subsequently provided him with a steady income for three decades.

"I first noticed Renee when we were both in a lecture on Salvador Dali at the Sorbonne and the first time I spoke to her was afterwards, at the metro station," he says, at last.

"I was attracted by her beauty, the fact that she was not French, that she was Jewish and that her skin was not white like most other European women, but darker," he says, adding that while Audrey Hepburn is generally seen as the "ideal woman" among Japanese, he has always preferred the Grace Kelly-type.

"For many nights, I had been inviting prostitutes back to my apartment, but not for sex," he says. "I wanted to eat them.

"Every time they used the toilet and had their backs to me, I had the gun but I could not pull the trigger. It was not for a moral or religious reason; I was scared that by pulling the trigger I would be giving in to my desires.

"But it was more than a desire - it was more of an obligation. It was something that I would have to do in the end. That's the thing about an obsession; it means that whatever your brain or body tells you to do, you have to do it. You become a slave to your obsession."

Over a period of weeks, Sagawa managed to spend more and more time with Hartvelt, discussing art and drinking coffee in Parisian cafes. He bought a carbine from a hunting shop.

Eventually, on the pretext that he needed a poem recorded for a class, he convinced her to accompany him to his apartment.

"She was standing at the sink, washing her hands, with her back to me, and I just had images of the prostitutes with their backs to me," Sagawa says. "The wheels of delusion in my mind started to spin and it was like the scenario I had been through so many times in my head.

"It's still a mystery to me how so much of my life has not gone according to plan, but that day did. I feel bad for saying it, but it went so well."

Sagawa put the rifle to the back of Hartvelt's head, took a deep breath, exhaled and pulled the trigger.

"She fell over onto the table, there was blood on the poem that she had been reading and the tape recorder, but then she slipped onto the floor," Sagawa recalls. "I jumped back and watched her face turn completely white - then I thought 'What have I done?'

"It was the first time I had seen a dead body and I was really shocked."

Sagawa's Jekyll-and-Hyde personality is apparent as he claims his first thought was to call the police and an ambulance. But the next thing he recalls doing was trying to wipe up the blood - "there was so much blood" - and taking her clothes off.

"I wanted to eat her buttocks, but I had to flip her over and she was heavy," he says. "I tried to bite into her buttocks, but the flesh was too hard. I tried to use a fruit knife, but that didn't work either, so I went out and bought a curved knife."

That implement had the desired effect. He describes in chilling detail how he carved open Hartvelt's buttocks, cut through the layers of fat "and eventually clawed out the red meat".

"A lot of people ask me what it was like and I do not usually like to answer that question because it was just so delicious," he says. "I can recall it now. It was like the best tuna, without the smell."

Sagawa says that in moments of clarity he was repulsed by his actions; but then he had sex with the corpse.

"It's funny, but I can't remember her face now," he says. "I can't believe that."

Sagawa says he did not want to eat the entire corpse - but over the next couple of days he sliced off parts of the body and stored them in his fridge.

Photos later released by the French police to the media are, quite simply, horrific. In black-and-white - a small mercy - they show graphically what Sagawa did to Hartvelt's remains and the plates of meat he prepared for consumption.

Caught attempting to dispose of body parts in a suitcase in the lake in the Bois de Boulogne public park, Sagawa was arrested and held without trial for two years while psychologists examined him and a top lawyer retained by his father argued that he was legally insane. The French court accepted that claim and declared him unfit to stand trial, ordering instead that he be held indefinitely in a mental institution.

Sagawa used his time behind bars to write In the Fog, an account of his actions, and his father's legal team quickly convinced the French authorities that he would be better cared for closer to his family, in Japan.

Back in his homeland, Sagawa was sent to Matsuzawa hospital and interviewed by psychologists, who disagreed with their French counterparts, found their subject to be sane and declared that sexual perversion was the sole motivation for his actions.

So, deemed to be sane and never found guilty of a crime, in August 1986 Sagawa simply walked out of the mental hospital, and found his insight and experiences immediately in demand.

Over the following years, he became a celebrity, writing 18 books, regular newspaper columns and restaurant reviews. He was also invited to appear on television cooking shows and happily played along when asked to sample slices of raw meat. And he appeared in the low-budget porn film Unfaithful wife: Shameful torture, in which he bites the buttocks of the actress.

As the memory of his crime has diminished, however, Japan's media has moved on.

Sagawa's latest book, Shinjuku Gaijin House, charts the adventures of a group of foreign residents of one of Tokyo's sleaziest districts. Released in July last year, its sales have been disappointing, and he claims he struggles to get by.

Attempting to distance himself from the events of Paris has clearly not paid off. His books don't sell. He is not being invited back onto the celebrity chat shows. An invoice on the kitchen table is from a food delivery service provided by the city council.

"It's hard," he says, his eyes tearing up once again.

If they can bear to think of him, Hartvelt's family may take some satisfaction from the fact that the man who caused them so much pain is experiencing some discomfort of his own. It is, after all, the only justice they will ever get for their daughter.

But before our conversation is at an end, Sagawa's other face returns and he admits he will never be free of the urge to eat women, an urge he first had at the age of five and which he can trace back to a dream of being chased by his parents, who wanted to eat him.

"I have the same desires today, of course," he says. "They will continue until I die. I like elegant women. I like intelligence and beauty. And when I am able to see all of that in one person, then I cannot help but wonder what she might taste like."