KRX Cut NXT's Evening Turnover. Total Share Recovered.

Nextrade's share of South Korean stock volume fell to 9.10% during the first eight sessions after the Korea Exchange opened a competing evening market, from 10.64% in the nine sessions before launch. Then the result changed. NXT averaged 11.34% in the final five sessions through 2 October, above its pre-launch mark.

The full 13-session result is less dramatic. Calculations from NXT's official daily series put its average volume share at 9.96%, down 0.68 percentage points from the pre-launch period. KRX won the opening round. It did not dislodge the challenger.

The split between whole-day share and evening turnover explains why. NXT's average daily after-market value fell 39.5% to KRW1.67 trillion after 14 September, from KRW2.76 trillion. Its total venue share nevertheless recovered late in the observation window. Broker routing and session continuity are plausible mechanisms, but the public series cannot measure their contribution against stock mix or changing market conditions.

A broader stock list did not settle the contest

KRX replaced its 16:00 to 18:00 ten-minute call auction with continuous trading from 16:00 to 20:00. The regular 15:30 close stayed in place, and after-market trades retained T+2 settlement. The base universe covered 2,765 KOSPI and KOSDAQ stocks and depositary receipts. A launch-day report citing KRX put the eligible list at 2,501, with 2,413 traded, and counted 38 participating brokers representing 95.2% of brokerage market share. KRX's rules and launch reporting confirm that ETFs, ETNs and securities under specified market controls remained outside the session.

That breadth produced far more shares, but not more money. On launch day KRX traded 72.24 million shares worth KRW1.8177 trillion, while NXT traded 12.17 million shares worth KRW1.7896 trillion in its after-market, according to KRX data reported by Chosunbiz. During the first week, NXT's after-market value totaled KRW7.24 trillion against KRX's KRW5.74 trillion, according to KRX figures reported by Financial News.

The difference is stock mix. NXT concentrates on roughly 600 liquid names, while KRX added a long tail of lower-priced KOSDAQ stocks. A raw share count therefore flatters KRX's reach and understates the economic weight of NXT executions. The pre-launch figures made the same point in reverse: NXT held 37.46% of combined trading value from 1 July to 9 September, but only about 18% of average volume, according to Yonhap. Those are different measures, not rival estimates of one market share.

The evening book weakened while total share recovered

NXT's official figures cover nine sessions from 1 to 11 September and 13 sessions from 14 September to 2 October. Its average daily volume fell 10.3% after launch, to 98.36 million shares. Average value fell 20.7% to KRW10.39 trillion.

The direct overlap suffered more. After-market volume fell 45.5% to 11.38 million shares a day. After-market value fell 39.5% to KRW1.67 trillion. NXT's evening session also begins at 15:40, giving it a 20-minute head start over KRX, so these totals are not a strict 16:00 to 20:00 comparison.

The first eight sessions looked like a durable share loss. The final five did not. NXT's daily volume share ranged from 9.36% to 13.11% in that later block and averaged 11.34%. Yet its evening value remained well below the pre-launch baseline. The late recovery in whole-day share cannot be presented as proof that NXT won back the evening. The public series does not isolate whether the rebound came from pre-market trading, main-market activity, order continuity, stock mix or broader market conditions.

Routing policy is part of market structure now

South Korea's best-execution rule lets investors name a venue. If they do not, brokers compare price, available quantity, fees and execution probability. Kakao Pay Securities' current notice says its integrated orders compare the two books and may route to the venue expected to resume first when one enters a volatility auction.

Order continuity creates a second decision. KRX cancels regular-session orders at 15:30 rather than carrying them into its after-market. NXT runs a one-board structure that can keep an order alive across its main and after-market sessions. KB Securities tells clients that an unmatched KRX order must be canceled and re-entered for either evening venue. During simultaneous auctions, its routing rules favor the market that started the auction first; ties and market orders go to KRX.

That is not a neutral pipe. A passive order already resting on NXT has queue position and no resubmission gap. A new order at 16:00 can reach KRX's broader list. A taker should follow the better displayed price and total consideration. A maker depends on queue, spread and fill probability. Stock coverage attracts possible orders. Session design and router settings determine which become trades.

More trading is not yet better price discovery

The new session produced a warning on day one. KRX recorded 1,637 volatility interruptions after the regular close, against 400 during the regular session. Some 65.1% occurred in the first 30 minutes and 80.1% in the first hour. Thin books were finding prices, but not smoothly.

The disclosure gap remains untested. Formal filing hours still end at 18:00, two hours before trading closes. KRX can halt a stock when severe delisting-related facts emerge through credible reports after the cutoff, and NXT mirrors KRX market actions. Public venue statistics do not yet provide a matched series for post-18:00 halts, quoted spreads, order-book depth or next-open reversals.

Volume alone cannot establish that the extra two hours improved price discovery. The defensible result after 13 sessions is narrower. KRX cut into NXT's evening turnover, while NXT's total share recovered. The public series does not isolate how much routing, session continuity, stock mix or market conditions contributed. The lasting contest will be measured in spreads, fills and next-open price continuity. The early evidence shows that neither copied hours nor a larger menu produced a decisive win.