A woman looks at manga displayed at the Tokyo International Anime Fair in March. (Yuriko Nakao/Reuters)

Tokyo politicians are toughening up regulations governing the sales and rental of manga — Japanese comics and graphic novels — and anime films in an attempt to prevent minors from accessing material that references extreme sex acts or crimes.

The city's metropolitan assembly approved on Wednesday a revision to an existing ordinance dealing with "the sound upbringing of youth."

The revision concerns manga or anime containing depictions of extreme sexual acts involving underage-looking characters (including rape, incest and other sex crimes). Such material will now be banned from sale or rental to those under the age of 18.

The amended legislation includes a clause stating that the assembly would take into account a work's "artistic and social expression" in considering which titles will be restricted.

The city government set an April 1, 2011, deadline for the manga publishing industry to begin regulating itself and toning down extreme sexual content. Retailers must also comply with the age restrictions — for instance by moving works into adult-only sections — beginning July 1, 2011. Those found breaking the rules will be fined.

Highly popular, lucrative industry

Manga is a multibillion-dollar industry in Japan, producing scores of graphic-heavy publications that explore a wide range of topics — eagerly read by both children and adults.

Titles range from kid-friendly cartoons and adventure tales to complex adult-oriented material that — like novels — explores myriad genres, including historical or contemporary drama, comedy, romance, fantasy, science fiction, crime thrillers and even erotica.

Prominent manga artists, retailers and a coalition of the 10 major publishers have blasted Tokyo's revised "sound upbringing of youth" ordinance as a limit on freedom of expression.

In protest, the publishers' group has vowed to withdraw its participation in next year's highly popular and government-sponsored Tokyo International Anime Fair, set to take place in March. Considered one of the world's largest anime-related events, the fair draws in excess of 100,000 visitors.

The initiative to restrict manga containing extreme sexual content was introduced in spring 2010. However, the bid was voted down in June following vigorous protest from artists and publishers, as well as criticism from some politicians that the regulations were too vague.

Shintaro Ishihara, Tokyo's conservative governor, has been joined by parent and teacher groups in campaigning for legislation restricting sexually explicit manga.

In comments made this week, Japanese Prime Minister Naoto Kan urged the two sides to find a middle ground.

"Sound upbringing of youth is an important subject," Kan wrote on his official blog.

"At the same time, it is important to export Japanese animation to the world. I would like to see those concerned co-operate so as to avoid any possible situation which would hinder Tokyo from hosting an international anime fair."