Human sexuality is a powerful and mysterious thing, and sometimes it seems just outright bizarre.

No one knows this better than 50-year-old Nobuhiro Komiya who for the last two years has worked tirelessly doing one of the most unlikely and mind boggling of jobs - censoring the unending torrent of hentai manga or pornographic comics which flood Tokyo's book shops and convenience stores.

"It's a tough job.

"People who don't understand the nature of what we do here often say to me: 'I envy you; I wish I could read comic books for a living', but in reality it is not a lot of fun.

"It's totally different to reading manga as a hobby," he says.

A visit to the Department of Youth Affairs and Public Safety on the 35th floor of Tokyo's towering Metropolitan Government building, where Komiya and his small team of censors get down to the grisly task of comic book censorship, reveals we are talking about a lot more than the width of Wonder Woman's bust.

Spread out over the white Formica table-top are the worst of the worst - a hand-picked selection of the weirdest and most shocking examples of hentai from the country which invented it.

Page upon page of black and white etchings of wide-eyed, young people of indeterminate age drawn in that larger than life Japanese cartoon style, engaged in every kind of sexual act, legal or otherwise.

"Normal sex doesn't sell well," Komiya remarks.

"School sex, tied-up sex, abnormal sex, sells. So this is what they draw.

"Mangaka don't draw this stuff because they want to expose children to sexual perversity, they draw it for one reason: to make money."

Komiya doesn't pull any punches when it comes to talking about what he sees as Japan's mercenary and profit orientated comic book publishing industry.

A battle has broken out between the industry and the Tokyo Metropolitan Government - the Department of Youth Affairs and Public Safety, where Komiya works, is the front line of this war.

In December last year the Metropolitan Government, under the leadership of Tokyo's conservative Governor Shintaro Ishihara, pushed through a by-law that significantly tightens existing restrictions on selling manga with sexual content to young people.

In response 10 Japanese publishing houses, including big-name publisher Kodansha, announced they would boycott the Tokyo International Anime Fair and hold a rival fair called the Anime Contents Expo.

The Tokyo International Anime Fair, held in March, is one of the biggest events on the world anime calendar and is attended by thousands of otaku (fans) from Japan and across the globe.

The fair's organising committee is chaired by Governor Ishihara, so by boycotting the event the anime industry has been able to enact public revenge upon the man who is trying to censor them.

The new by-law, which is really a revision of the old existing regulations, specifically, aims to regulate manga which "unreasonably lauds or exaggerates" what they term "extreme" sex; in other words comics which encourage minors to engage in sexual activities which would be illegal for people under 18 to carry out.

"We are afraid that young people reading manga which encourages illegal sexual activity will lose their sense of judgment about what is healthy behaviour.

"They will learn to think that rape and incest are normal.

"We need to regulate these kind of manga and put them in a place in the store, such as the adult corner, where it is harder for kids to see and buy them," Komiya says.

"We are not telling people to stop producing sexually indecent manga; we are just trying to move it to the adult corner," he says.

Komiya acknowledges that many factors can affect the development of a child's sexual values as well as exposure to pornography, especially parenting and education, but he believes hentai manga has a big influence on Japanese youth.

Tokyo gynaecologist and advocate for manga censorship, Dr Tsuneo Akaeda, believes the style of pornographic manga is dangerous to youth.

"It's a kind of hyper-reality sex," he says.

Akaeda runs a women's clinic in Roppongi, one of Tokyo's famous nightlife districts popular among foreign tourists and ex-pats, and he has seen his fair share of sexual problems among young Japanese.

He puts this down in part to the influence of manga and adult videos.

"Manga only depicts sex as interesting, fun, pleasurable and enjoyable. There is no information about the dangers or risks involved in sex.

"Young Japanese think having an abortion after getting pregnant is a simple solution, but it involves high risk to the women," he says.

He adds that STDs, such as HIV and herpes, are also on the increase in Japan and condom use is declining - trends he blames on the influence of pornography on the young and the lack of proper sex education.

"Condom sales in Japan have fallen from 700 million sold per year to 200 million.

"Condoms are never shown in adult videos or manga," he says.

Tokyo lawyer and free speech advocate, Takashi Yamaguchi, believes the Tokyo Metropolitan Government and its supporters are unfairly placing blame on Japan's anime industry for sexual problems among the young.

He also worries that the new by-law may open the door to the censoring of a wider range of subjects, such as depictions of criminal activity in general.

"What about violence? What about organised crime? What about narcotics?

"It gives them a reason to expand it [the regulations] later.

"Right now it is limit to just sex, but if you take the standpoint that depicting crime [in a comic book] is harmful for children then anything could be justified.

"I think the Tokyo Metropolitan Government is taking a very dangerous step," he says.

Yamauchi adds that comics which have educational value, such as historical stories, could also fall under the censor's knife and lead to a white-washing of history.

"What about historical stuff? We had no regulation against child prostitution in the Edo era (from the 17th to 19th Century).

"What if you depict that? Will that be allowed?"

Censorship of pornography in Japan is very liberal in comparison to the West, and with the exception of a seemingly arbitrary brushing or blurring out of genitalia in adult videos, magazines and comics, almost no censorship occurs based on the nature of the content.

Yamauchi acknowledges this system of censorship is in some ways meaningless and arbitrary, but he believes it is preferable to the western style system.

"Personally, I don't think any regulation is necessary for adult material between adults. If it is fiction then I think it is okay," he says.

Keiji Watanabe of the Japan Magazine Publishers Association believes manga should also be exempt from censorship because it is a purely imaginative fictional world without real people.

"Japan's child pornography laws are aimed at protecting the human rights of real, living children.

"Comic books are therefore not subject to these laws," he says.

"The concern is that [Tokyo's proposed restrictions] will be extended into Japanese law in the future," he says.

Comic business
* Japanese manga or comic books are a lot more than mere smut and the vast majority of them are not even remotely pornographic.

* The manga industry in Japan is worth US$4.2 billion per year and comic books make up 22 per cent of all written publications in Japan. Some manga titles can furnish sales figures that give Harry Potter a run for its money.

* The long running manga series One Piece, about a boy with elastic arms who searches the ocean for treasure with his crew of pirates, has sold 200 million copies.

* Holding equal status with regular books, manga are read as much by adults as children and cover every single topic or genre under the sun; ranging from serious literary or intellectual topics, to super hero sagas like Astro Boy, or the useful but dull Manga Guide to Calculus.

* Karl Marx's Das Kapital was recently released in comic book form and sits comfortably on the otaku's shelf next to graphic versions of Shakespeare's King Lear, Hitler's Mein Kampf and Tolstoy's War and Peace.

Comic index
* Manga - General term for any type of Japanese comic book

* Anime - Japanese style cartoons or animated TV shows and movies.

* Hentai - This refers to a weird or abnormal person or behaviour, especially if sexual in nature. Among English speakers the term is more narrowly used to refer to explicit pornographic Japanese style comic books or cartoons.

* Otaku - A cult follower or fan of Japanese comics or animation; a nerd or a geek.

* Akihabara - Akihabara, or Akiba as it is known by the faithful, is Tokyo's famous electronics district and the nerve centre of Japan's otaku, anime and manga subculture.

* Shonen manga - The most popular and largest comic genre in Japan encompasses a wide range of themes which are popular with young men such as sports, action and adventure.

* Yaoi or Boy's Love (BL) manga - A comic book genre depicting love stories between young men. These comics are popular with middle aged Japanese women.

- James Benson helped with translation