Where did JPYC's ¥4 actually trade? The Upbit listing dislocation, seen through executed DEX trades
What happened
According to Upbit's notices and price data (both from the exchange's public API):
- At 09:48 on September 17, Upbit announced the listing of JPYC and PYUSD. Trading was scheduled for 12:00, then postponed twice, to 15:00 and then 18:00.
- Trading opened at 18:00 with a first print of 12.00 KRW. The only trading limit was a floor (−10% from a reference of 8.81 KRW); there was no ceiling.
- The high of 37.60 KRW (about ¥4.1) printed between 19:20 and 19:25.
- At 18:44 Upbit announced it would add Kaia and Polygon deposits, and deposits opened at 19:23 (withdrawals later). The same notice added a caution that Korean users face restrictions in using JPYC's issuance and redemption window directly.
According to press reports, JPYC Inc. paused issuance reservations on Ethereum at 20:34 and on Polygon at 22:19 on the 17th, posting them as incidents, and restored them at 23:43 and 00:22 respectively. The cause is described as under investigation, and the company has not commented on any relationship with the price dislocation. In a written comment to press, JPYC CEO Noritaka Okabe said that the company always receives ¥1 at issuance and can therefore redeem regardless of the secondary-market price (NADA NEWS, September 18).
What follows is that sequence re-read against executed on-chain trades and issuance data.
Executed prices: the highs only printed in small trades
The data set is every swap between JPYC and a USD stablecoin in Uniswap's JPYC pools on Ethereum, Polygon and Avalanche from 09:00 JST on September 17 to 12:00 JST on September 18: 55,293 trades. Prices are computed from each trade's exchange ratio, not from order books or aggregator composites, with USD/JPY fixed at 155.58.
First, when the dislocation started, peaked and ended on each chain, measured on 15-minute volume-weighted average price (VWAP):
| Chain | Start (first 15-min bar with VWAP above ¥1.20) | Peak (15-min VWAP) | First 15-min bar back below ¥1.05 |
|---|---|---|---|
| Ethereum | 17th 17:45 | 17th 18:30 (¥3.14) | 18th 02:00 |
| Polygon | 17th 18:45 | 17th 19:15 (¥2.92) | 18th 02:00 |
| Avalanche | 17th 19:00 | 17th 19:45 (¥1.39) | 17th 21:00 |
Ethereum began moving at 17:45, before Upbit opened. Avalanche is sometimes reported as "not affected"; it in fact reached ¥1.39 in the 19:45 bar and was back by 21:00. An observation just after midnight would correctly show 1.00×; the difference is the timestamp.
The next table is the core of this piece: trades between 18:00 and 22:00 on September 17, bucketed by JPYC amount per trade, with the highest price in each bucket.
| Trade size (JPYC) | Ethereum trades | Ethereum high | Polygon trades | Polygon high |
|---|---|---|---|---|
| under 1,000 | 1,135 | ¥17.59 | 5,273 | ¥12.04 |
| 1,000–10,000 | 1,443 | ¥13.98 | 4,810 | ¥27.55 |
| 10,000–100,000 | 662 | ¥6.88 | 3,959 | ¥9.96 |
| 100,000–1,000,000 | 105 | ¥3.32 | 1,049 | ¥3.51 |
| 1,000,000 and above | 2 | ¥1.31 | 19 | ¥2.98 |
The reported levels, "about ¥6.07 on Polygon" and "about ¥4", never printed in any trade of 100,000 JPYC or more. The larger the amount moved, the closer the realized price stayed to ¥1. "Mint at ¥1 and sell at ¥4" did not work at size. Aggregator highs and 15-minute closes carry no trade-size dimension, so this cannot be read off a price chart.
The issuer side: the first mint in 62 days, and 9.9 billion after the recovery
Supply data published on ChainAnalyzer's issuer page (no login required) shows that JPYC's total supply did not change for 62 days after the mint of July 17. Over that period the circulating amount drifted down from 2.49 billion on September 1 to 1.90 billion on the 16th; demand appears to have been met from already-issued, not-yet-circulating inventory. There were no burns in the past 180 days.
On the day of the event there were seven mints totaling 12.48 billion JPYC (times in JST):
| Time | Chain | Amount | tx |
|---|---|---|---|
| 17th 21:37:59 | Ethereum | 0.59 B | 0x12478820…e6fa05 |
| 17th 21:39:06 | Polygon | 1.39 B | 0x192db9bc…147b2b |
| 18th 01:19:59 | Ethereum | 0.60 B | 0xe71dcaf2…dabfdb |
| 18th 03:19:11 | Ethereum | 2.50 B | 0xf474ea8a…58d3bf |
| 18th 03:20:28 | Polygon | 2.40 B | 0x811f1d94…bbaef6 |
| 18th 03:21:46 | Avalanche | 2.80 B | 0x2688ad75…8ddd8e |
| 18th 03:22:59 | Kaia | 2.20 B | 0xea30e35f…c35e9d |
Three things stand out when this is laid against the timeline.
- The first mint (21:37) came about an hour after the reported pause of Ethereum issuance reservations (20:34). "Issuance reservation" is a user-facing procedure; a mint is on-chain issuance. They are different layers, and the company has not explained the relationship, so here they are only placed side by side.
- The final 9.9 billion (03:19–03:23, on four chains at once) came about an hour after the executed VWAP on Ethereum and Polygon fell below ¥1.05 at 02:00. It reads less like meeting immediate demand and more like restocking on a scale larger than the pre-event total supply (8.81 billion), but that is an interpretation.
- Ethereum's circulating amount on the 18th, 1.203 billion, exceeds the pre-event Ethereum total supply of 1.113 billion. Without additional mints, demand on Ethereum could not have been met. That is consistent with the CEO's comment that "issuance surged and we ran out of inventory in the middle of the night", although the company has not said what "inventory" refers to.
One more point about how the pools were used. On the event day about 0.69 billion JPYC passed through Uniswap pools on Ethereum, roughly 19% of the 3.69 billion minted on Ethereum that day (and that figure is gross, including round trips). Inflow of 0.692 billion against outflow of 0.685 billion means the pools held no inventory; they were a corridor. Most of the new issuance did not go through a DEX in this window.
Why the corridor was narrow
If something mints at ¥1 and sells at ¥4, arbitrage should close the gap quickly. It did close, but it took eight hours on Ethereum and Polygon. Every factor cited in press coverage points to the same thing: the corridor between the primary market (issuance and redemption) and the secondary market (exchanges and DEXs) was narrow.
- At listing, Upbit supported deposits and withdrawals only on Ethereum, and Ethereum held about 7% of all circulating JPYC.
- Issuance is capped at ¥1 million per request, and consecutive requests in a short period are not accepted (JPYC Inc. release, May 2026).
- Using Upbit requires a Korean bank account; issuing or redeeming JPYC requires identity verification with a Japanese My Number card. Very few participants could complete "mint at ¥1, sell on Upbit" alone.
- The DEX pools that linked Japan and Korea were thin; as the table above shows, trades of tens of thousands of JPYC moved the price several-fold.
A similar listing-day spike in a euro stablecoin was reported on a Korean exchange in August, so this is not specific to JPYC.
One token, one day, three prices and three clocks
The same token from the same issuer peaked at ¥3.14 on Ethereum, ¥2.92 on Polygon and ¥1.39 on Avalanche on the same day, and recovered at 02:00 on the 18th, 02:00 on the 18th and 21:00 on the 17th respectively. With no official bridge, cross-chain arbitrage runs through the primary market, and the peg is maintained separately on each chain. For anyone settling in a stablecoin, which chain you receive it on is itself a risk factor.
ChainAnalyzer's issuer pages publish per-chain total supply, circulating amounts and issuance/redemption events for JPYC and other major stablecoins. Anyone tracking supply by chain can use /issuers/jpyc without logging in.
Method and limitations
- Prices are computed per trade from swaps between JPYC and USD stablecoins (USDC / USDT / DAI) in Uniswap's JPYC pools. USD/JPY is fixed at 155.58, the rate at 19:37 JST on September 17. Highs and lows are limited to trades of 50,000 JPYC or more, except in the size-bucket table, which uses every trade.
- Kaia DEXs are outside this data set; prices on Kaia were not observed.
- The pause and restoration times for issuance reservations are the values on which several press reports agree. JPYC Inc.'s website carries no notice, so they were not confirmed from a primary source.
- "Participants" are addresses, not people.
- Supply and circulating figures are ChainAnalyzer's own aggregation and differ in definition and timing from figures published elsewhere.
This article is an analysis based on public information and is not a recommendation to buy or sell any crypto asset.