Japan's greying population is changing the character of its beloved manga comics, spawning a new genre in which the elderly aren't pitiable oldsters but protagonists making discoveries, finding friends and sometimes even having hot sex.

Demand for stories focused on the elderly has grown alongside their audience: 27.7% of Japanese are older than 65, up from 21.5% just a decade ago.

Readership cuts across society, the publishers say, from retirees looking for plots they identify with to younger Japanese watching their nation age, with growing concern about their later years.

"Different social problems and concerns rise up as opposed to when society is centred around young people, and manga that show the reality of an ageing society are in demand from both readers and writers," said Kaoru Endo, a sociology professor at Tokyo's Gakushuin University.

Manga, both print and digital, pulled in 430 billion yen in 2017, according to the Research Institute for Publications. They're ubiquitous in daily life, showing up everywhere from crowded subways to coffee shops and waiting rooms.

Although no public data exists on the market share for senior-focused manga, the genre is clearly growing. Eight of the 11 most popular such works, according to industry insiders, started publication after 2014. Three were in 2017 and 2018.

"The over-60 generation - in whose youth manga gained wide acceptance - have loved manga since they were kids," Endo said.

Yuki Ozawa, illustrator of "Sanju Mariko," about an 80-year-old widow who sneaks out of her crowded family home to live on her own and write, thinks escapism plays a big role too.

"When you watch news about ageing, there are so many dark, serious topics. It makes people anxious," she told Reuters.

"There are also a lot of people who are single, who probably will never marry and always live alone, and when they're feeling gloomy they read Mariko and feel as if they've seen a ray of light," she said.

Virtually no topic has escaped manga since the medium took off about 50 years ago. There have even been manga on the 2011 earthquake and tsunami, including the Fukushima meltdown.

Elderly characters, though, were mostly peripheral: a loving grandma, somebody needing nursing care, a venerable sage.

Manga that did star the elderly, like an early '90s series about an aged heavy metal band, didn't always treat them as normal people.

"Seniors were there, but with an element of surprise. He might be an old man but he's really smart, a weird superhero," said Natsuki Nagata, an assistant sociology professor at Hyogo University of Teacher Education in the western city of Kobe. "It was if they were a different species."

But recent examples, such as Kaori Tsurutani's "Metamorphoze no Engawa" (Veranda Metamorphosis), bring a more human touch.

In that story, a septuagenarian widow and geeky teenage girl bond over homoerotic manga, building a friendship of text messages, cafe trips and manga fan events. Ozawa's Mariko may be 80, but the loneliness that prompts her to leave home is universal.

Characters are "being illustrated in a way that feels closer to reality," said Tsurutani, 36, who said memories of her late grandmother inform her work.

Challenging subject

Some manga in the genre use pure fantasy to attract readers while still touching on the often grim reality of elderly issues.

One series features a septuagenarian couple becoming parents, while in another an elderly woman and a teenage girl switch bodies.

"There are certainly a lot of social problems involving the elderly, and they're very serious," said Ozawa, whose Mariko has no health issues and a steady income - uncommon even in a nation with vigorous seniors. "But to write just about that means readers will only pay attention to the social issues, and it'll be a bit depressing."

Illustrator Kenshi Hirokane, whose "Kosaku Shima" series about a businessman has run since 1983, shows its hero rise from section chief to chairman of his electronics firm, ageing realistically over the years.

Hirokane in 1995 also launched "Like Shooting Stars in the Twilight," one of the earliest senior-centred manga. A drama of older peoples' lives and loves, it also includes some hot sex scenes.

"I wanted to write about ordinary men and women having an ordinary love," the 71-year-old Hirokane said of the series. "Readers want topics that are close to them."

Hirokane's prize-winning series now has 58 volumes.

"As many people age, they lose their dreams and hopes, they think there's nothing more they can do. No, it's not like that at all - you can still fall in love, you can still do lots of things," he told Reuters in his western Tokyo studio.

In demand

Rikiya Kurimata, a bookseller at Tsutaya, one of Japan's largest bookstore chains, said the genre's readers span generations and genders. Recently, they have been asking for "manga about the elderly" as well as specific titles.

"I think this trend won't just continue but grow. Supply still hasn't met demand," Kurimata said. "Right now we don't have a special section for the genre, but if things go on like this, we'll have to make one."

A half-million copies of Sanju Mariko, both print and digital, have been sold since its debut in 2016. Tsurutani's first volume has gone through five additional printings since May.

Atsuko Ito, 66, a farmer from northern Japan, says she enjoyed Hirokane's series for the way it highlighted the ups-and-downs of life.

"It feels as if life itself is drawn there, with things that we all have experienced - and some we haven't - which makes me empathise," she added. "Then sometimes when a main character makes a decision I think, 'I can do that too', and it gives me courage for my daily life."

That sense of humanity is at the heart of the genre's success, Endo said. "What the manga say is, people are the same underneath - and this teaches young people not to be afraid of either the aged or ageing," she said. "We all have the same feelings, young or old."