The district of Ikebukuro is known as a subcenter of Tokyo along with Shinjuku and Shibuya.
Although Ikebukuro is popular among young people partly because of the nearby Rikkyo University campus and the Sunshine 60 skyscraper building, there was deep shock in Toshima Ward, which includes the Ikebukuro district, in May last year.
Toshima was the only one of Tokyo's 23 wards that was listed as a municipality that could disappear as a residential area in the future.
The municipalities were predicted to see a drastic decrease in the number of young women, which could make administrative services impossible to provide.
The ward office felt a strong sense of urgency and has made full-fledged efforts to promote Ikebukuro.
First, it promoted the district as an anime centre for women. There is a street there called Otome Road, where stores with specialty goods related to anime and comics for women have increased in number.
There has also been a rise in other kinds of stores for women. Otome Road became popular and thus anime fans pay great attention to the area.
The ward office has picked up on the trend: Toshima Ward Mayor Yukio Takano participated in a Halloween event in October last year, dressing as a number of popular anime characters.
And an event for female anime fans in November last year, held in co-operation with the ward government, attracted 30,000 fans in two days.
Sayaka Watanabe, a 22-year-old anime fan who visited Ikebukuro from Saitama Prefecture, said: "I got so excited just being here. I can't imagine this area would disappear."
She had previously enjoyed going to the Akihabara district, but now "I absolutely prefer Ikebukuro," she said in a serious tone.
In co-operation with private-sector entities, the ward office has implemented a series of unique efforts.
They include gatherings of local female residents to discuss how to create better living conditions where people raising children can feel comfortable, lectures about how to utilize real estate to attract young people as customers, and concerts that infants under the age of 1 can attend.
A section chief in charge of projects at the ward office takes a proactive position on the shocking prediction.
"The prediction pointed out the future risks to this ward, so we can use it as a springboard to raise the levels of our administrative services," he said.
Will the day come when the ward can wipe out its image as a city with the potential to disappear?