In June, the popular online flea market, Mercari Inc., is expected to be listed on the Tokyo Stock Exchange’s Mothers section, which is reserved for high-growth startup companies. According to an article in the April 18 Asahi Shimbun the value of the company’s stock at the time of the listing could exceed ¥200 billion ($1.8 billion), making it the highest new listing of the year on Mothers. The company hopes to use the funds to expand into overseas markets.

Mercari, which has been in business since 2013, is one of the most successful Japanese startups of the decade. The concept is simple. People who want to sell items they no longer need can post those items on Mercari and other people can buy them directly from the seller in a peer-to-peer arrangement. Transactions can even be carried out through a stand-alone app, which means buyers and sellers can use the service via their mobile devices.

Unlike auction-type sites such as eBay, the seller sets the price (though buyers can bargain). Sellers also handle the shipping themselves. Mercari adds a surcharge for its role in the sale. When a transaction occurs, it withdraws money from the buyer’s preregistered account but does not transfer it to the seller’s account until after the buyer receives the item and evaluates it. When everyone is satisfied, the seller receives the money. Basically, Mercari is a kind of market space where vendors set up shop. But unlike conventional online shopping malls, like Rakuten, anyone can be a vendor as long as they become a member, even if they’re only selling one item.

Apparently, the company still needs to address some ongoing problems with the service. In December it started adopting measures to solve the issue of illicit sales of stolen goods on the site, by reinforcing identity checks.

A follow-up article in the Asahi reported that the market size of domestic online flea markets in 2017, according to an estimate by the Ministry of Economy, Trade and Industry (METI), were ¥483.5 billion — a 58 percent increase over 2016. About one in six Japanese people between the ages of 15 and 69 have used a flea market website or app. As a proportion of all internet retail sales, those for secondhand goods made up 5.8 percent in 2017 — the highest ever — and METI predicts the sector will continue to grow due to increased use of smartphones and the ease of use of flea market apps.

However, a more significant reason for the predicted increase in penetration of Mercari and other flea markets is changing attitudes toward shopping itself, not to mention the very idea of what it means to purchase something. Two years ago, the Environmental Ministry carried out a survey asking people if they had ever bought secondhand clothing. They found that women in their 20s and 30s are much more likely to have bought used clothing than men who are over 40. Asahi pointed out that until now there have been few studies carried out on the market for secondhand goods. But if business people really want to understand buying trends among young people today, they have to include secondhand retail, because the growth potential is enormous thanks mainly to the emergence of flea market apps like Mercari.

People under 30 are sometimes referred to as the “digital native generation,” meaning they grew up with the internet as a central element in their lives. When digital flea markets appeared, they were already prepared to use them. At the end of last year, Mercari reported that a million new items a day were being posted on its site. In a single month, Mercari transactions amounted to ¥10 billion in sales. Mercari’s president, Fumiaki Koizumi, pointed out to Asahi that the appeal is about more than just making money. He says people gain a sense of “pleasure” when putting their possessions on his site and selling them, because those items are evaluated by others in a positive way when they pay for them. The transaction satisfies the seller’s “desire for approval.”

But this ease of conducting transactions is also affecting the way young people think about their purchases. Hikaru Yamamoto, an assistant professor at Keio University’s graduate school, studied Mercari users, and found that more than half compare prices of new items to those of comparable secondhand goods being sold on flea market apps before they purchase a new item. This sounds like common sense, but the reason for the comparison seems to be different from what most people might think. In many cases, the buyer wants to gauge the markdown on the secondhand item they are thinking of buying, because after purchasing, say, a piece of clothing, they may wear it for a time and then sell it themselves. As Koizumi said to Asahi, this aspect of Mercari sales makes users feel as if they have a “large, shared wardrobe.”

METI estimates the peer-to-peer secondhand merchandise market in 2016, not counting automotive goods and housing, was ¥1.9 trillion. More to the point, they estimate that the value of purchased items that people say became “unnecessary” in the past year, excluding automobiles and motorcycles, is about ¥7.6 trillion. As a point of reference, the yearly sales of Japan’s biggest retailer, Aeon, is ¥8.5 trillion.

To older people, the idea of shopping is directly related to ownership: You purchase something and it is yours, and regardless of whether you think you need that item, you probably hold on to it. Younger people, however, are less concerned about ownership, less interested in possessing things than they are in “using” or even sharing them. This mindset is exemplified most vividly in the increasing dominance of streaming services for music and the spread of e-books. Young people are less likely to think of music and reading materials as things, or, at least, as things that they put on the shelf.

That thinking has been extended to apparel. A service called AirCloset sends members — which at the moment seems to be restricted to women — several outfits a month that they wear and then return. Using algorithms based on questionnaires the company determines the kind of clothing the member will like and need, thus removing even the element of choice (but not surprise) from the transaction. While this idea does break the stereotype of the shopping-obsessive, it also bolsters the primacy of fashion, which, by definition, changes with the seasons.

But there’s another aspect to the secondhand merchandise market that is having a profound impact on retail, and that’s the rapid aging of society. Boomers were the first generation of Japanese who were able to buy anything they wanted, and they accumulated a lot of stuff. They are now dying, and that stuff must be reckoned with. Secondhand stores and flea markets are being flooded with things that these boomers’ heirs are trying to get rid of.

Most of the time they don’t even bother and give the stuff away in bulk. Entrepreneurs have carved successful businesses out of this social phenomenon. An article in the March 20 Chunichi Shimbun described auctions in the suburbs of Manila where secondhand items from estates in Japan are sold to local retailers for good money. Merchants collect items from homes of the deceased and hire containers to ship them to the Philippines, where they are considered valuable not so much because they are “made in Japan,” but because they were “used in Japan.” The idea that a discerning Japanese consumer owned these items is a potent selling point for Philippine consumers. Sometimes being pre-owned can actually make an item more precious, but it depends on the owner.

Yen for Living covers issues related to making, spending and saving money in Japan.