Tokyo, Japan – While walking his toy poodle in the park near his home in Ikeda, Gifu Prefecture, Shin Ohta had an idea.

“My dog often stops walking during our strolls. I would carry him every time, but his weight of nearly 5kg [11lbs] started to become a real burden,” Ohta told Al Jazeera.

“I knew there had to be a better way.

Ohta works in sales for Japan’s oldest baby carrier manufacturer, Lucky Industries, which has produced more than 40 million baby carriers since its founding in 1934.

He has spent his career making baby carriers, but after that walk, he wondered if the same expertise could be applied to pets.

After consulting a veterinarian to ensure the design was viable for dogs, Ohta helped Lucky Industries launch its first line of dog hip carriers in 2022: Nu-i.

Earlier this year, the company joined dozens of other brands at Tokyo’s annual Interpets conference, a showcase of Japan’s rapidly growing pet care market.

During the first weekend of April, stalls lined the walls of the Big Sight convention centre, selling everything from walk-in pet dryers to the latest organic cat treats.

Few of the pet owners attending the event had their four-legged friend on a leash, instead ferrying them to and fro in well-decorated pet strollers, or the doggy equivalent of baby slings.

Many pets were decked out in colourful outfits, fur clips, and diapers.

Pets in Japan now outnumber children under 15 by more than 2 million.

According to market intelligence company Euromonitor, the country’s pet care market was worth 880 billion yen ($5.4bn) in 2025, up from 689.6 billion yen ($4.2bn) in 2020.

As Japan’s birthrate continues to fall and the population of children shrinks, companies that once built their businesses on babies, selling nappies, slings, and strollers, are increasingly turning their attention to pets.

Betting on pets at the Interpets conference, Unicharm’s expansive stall was lined with dog and cat nappies from its latest “Mannerware’” line.

The Tokyo-based company has been one of the great cross-market successes of the pet care boom.

After making its name selling feminine hygiene products and disposable diapers, Unicharm expanded into pet diapers in 2001.

Since then, pet care products have become one of the company’s main growth engines.

While the personal care market for people is larger, the pet care sector has higher profit margins.

According to Unicharm’s financial results for 2025, the company’s pet care division had a profit margin of 15.4 percent that year, compared with personal care’s margin of 10.7 percent.

Isshu Uehara, a Unicharm spokesperson, said that as of 2025, the pet care business accounted for 17 percent of the company’s total sales, with plans to increase that share to 20 percent by 2030.

“Japan’s birthrate is declining,” Uehara told Al Jazeera.

“Lifestyle changes, such as remaining single, marrying late, and the growth of childless, dual-income households, have led to a greater number of people seeking emotional connections through pets.

“As a result, we’re seeing the growth of ‘pet humanisation’, or treating pets like family members or children rather than just animals.

“Customers want to buy premium products to extend pets’ lifetimes, and share experiences with them, like dining together or going out to cafes and friends’ houses,” Uehara added.

Unicharm is not alone.

Across Japan, stroller brands like AirBuggy and clothing companies like Sweet Mommy have made similar leaps, applying expertise built around infants to a growing market of pet owners.

Lucky Industries CEO Hiroyuki Higuchi pointed to the company’s origins to explain the shift towards pets.

“When the company started, Japanese families had many children, and mothers needed carriers to be able to work around the house,” Higuchi told Al Jazeera.

But now, Japanese families are shrinking. While there has been a rise in single-person households and childless dual-income households, families with only one child have become more common as well.

A national survey of fertility trends found that between 2002 and 2021, the proportion of households with only one child increased from 10 percent to nearly 20 percent.

“With fewer babies around, it has been harder to come up with new ideas for baby products,” Ohta said.

“Now, my life is centred around my dogs, as are the lives of many of my friends. When we meet up, we talk about our pets.”

“Compared to the baby goods market, the pet sector is doing better,” said Higuchi.

“Companies see it as a reliable sector… In Japan, dogs are seen as babies, as part of the family. Just like many Japanese carry their babies in slings or carriers, so can dog owners,” Higuchi added.

Barbara Holthus, a sociologist and director of the German Institute of Japan Studies, said pet humanisation has been a growing trend in recent years.

“Before, a dog or cat might have just been an additional family member, but with fewer other family members and fewer children in the house, the focus becomes very concentrated on this animal,” Holthus told Al Jazeera.

“But it’s more diverse than just replacing children. Animals take on many different roles,” Holthus added. “A pet can also replace a partner. After a divorce, people sometimes get pets.

After someone gets widowed, they get a pet. Sometimes, a pet is seen as a play partner for an only child.”

Holthus sees Japan as a prime example of changing family structures, including the emergence of the “multi-species family”.

Holthus said decreasing birth rates, as well as factors such as loneliness and rising urbanisation, help explain why the trend of humanising pets has been particularly pronounced in Japan.

As for why infant brands are turning to pets, Holthus offered a simple explanation.

“It’s understandable,” she said.

“Of course, companies want to make money, and due to demographic change, their market is getting lost.”