JPYC, the first yen stablecoin licensed in Japan, opened on Upbit on September 17 and briefly traded at about four times one yen. The token is meant to hold a 1:1 peg, backed by government bonds and bank deposits. On the Korean won book it did not.

Upbit announced the listing at 09:48 KST, alongside PayPal’s PYUSD, on won, bitcoin and tether markets. Trading was set for noon, then pushed to 15:00, then to 18:00. It opened at 12 won. The reference was about 8.81 won per yen. The only limit was a floor, 10% under that reference. There was no ceiling. Between 19:20 and 19:25 the print hit 37.60 won, about 4.1 to 4.2 times the peg, with the won-yen rate near 8.85. By late afternoon it was back around 8.64 won. First-day volume was about 285.9 billion won ($207 million). A day later it was under a tenth of that.

The gap was a plumbing problem, not a yen problem. Deposits opened on Ethereum only, and Ethereum held about 7% of circulating JPYC. Polygon and Kaia deposits were added at 19:23; withdrawals came later. Issuance is capped at 1 million yen per request, and consecutive requests in a short window are refused. Minting needs a Japanese My Number check. Trading on Upbit needs a Korean bank account. Almost nobody could mint at one yen and sell into the spike alone. On-chain, the four-yen prints were small tickets. Across 55,293 DEX trades on Ethereum, Polygon and Avalanche, highs above a few yen sat in clips under 1,000 JPYC. Trades of 100,000 JPYC or more topped out near 3.3 to 3.5 yen. Trades of 1 million or more were closer to 1.3 to 3 yen. The issuer then minted. After 62 days with no mint, seven mints from 21:37 on the 17th through 03:23 the next day created 12.48 billion JPYC, most of it after the price was already back near the peg.

Seoul noticed. Yoo Young-joon, director of digital finance policy at the Financial Services Commission, said the commission would look at market-making so a listing spike does not become a user loss. The Virtual Asset User Protection Act has no exemption for market-making inside its manipulation rules, so a desk that quotes both sides is not clearly legal. A won stablecoin is still stuck: the Bank of Korea and the FSC have not agreed who may issue one, and the next digital-asset bill is expected in parliament in November.

The same week maps the rest of the region. Tokyo has a licensed yen token. Hong Kong’s Stablecoins Ordinance has been in force since August 2025, and the HKMA granted the first two issuer licences in April 2026, to HSBC and Anchorpoint. Beijing, in a February 6 joint circular, barred unauthorized yuan-linked stablecoins onshore and offshore. Korea has the exchange, the volume and the retail bid, and no local issuer. JPYC’s licence sets the mint price in Japan. It does not set the book on Upbit.