Investment & Economy
The day KOSPI jumped 17%, my indicator flashed buy too
As KOSPI and KOSDAQ rebounded violently and SK hynix hit its upper limit, I reconsidered the meaning and limits of a signal I originally built for crypto.
Summary
At a glance
- I saw the double-digit rebounds in KOSPI and KOSDAQ and SK hynix's upper-limit close as reasons for caution, not simple relief.
- My Pine Script indicator, designed for crypto volatility, produced its first buy signal since early last year, but I remain skeptical of its predictive value.
- I admit regretting that I missed SK hynix, while choosing to record my entry reason and risk boundary before trusting any signal.
This is a personal record of my investment process and opinions. It is not a recommendation to buy or sell any security, and neither the indicator nor the views below should be used as investment guidance. Every investment decision and outcome remains the investor’s responsibility.
The numbers from July 31 look like a rebound in the most literal sense. KOSPI closed at 6,595.45, up 17.91%, while KOSDAQ rose 11.63% to 719.76. SK hynix reached its daily upper limit, closing at KRW 1,718,000 after gaining 29.95%. Those are unusually large figures to fit on one screen and one day.
My first reaction was not relief. A market that rises sharply after falling sharply has not necessarily become safe. It felt like an elevator had fallen, bounced into the ceiling, and been declared operational because it was going upward again. My motion sickness was still doing business as usual.
I noticed volatility before I noticed recovery
On KOSPI, 775 stocks advanced and foreign investors were net buyers of more than KRW 7 trillion. KOSDAQ recorded 1,557 advancing names. The rebound was broad, but the detail that stayed with me was KOSPI moving more than 1,000 points in a single session.
SK hynix’s recent closes make the picture even less comfortable. It closed at KRW 1,759,000 on July 24, then KRW 1,550,000 on July 28, KRW 1,401,000 on July 29, and KRW 1,322,000 on July 30. One day later it finished at KRW 1,718,000, its upper limit. The speed is too great for me to pretend that investors collectively revised the value of the same business with calm precision every day.
I therefore see this session less as confirmation of direction and more as confirmation of risk. A screen changing from red to green does not remove volatility. I would not release the safety bar simply because the roller coaster had started climbing.
A crypto indicator has become busier in Korean equities
I once wrote a simple Pine Script indicator to support my cryptocurrency trading. I designed it with highly volatile assets in mind, trying to catch broader states of overheating and reversal rather than every small movement. Lately it has been working harder on Korean stock charts than on crypto. As a developer, I usually like improved performance. This is not the kind of performance improvement I wanted.
According to my records, the indicator produced a buy signal early last year and then kept showing sell-side signals. It has now displayed buy again. The green triangle naturally caught my attention, but if I am asked whether it marks a meaningful turn, my answer remains skeptical.
A capture of the reference-only Pine Script indicator I built. The KRW 1.69 million shown was an intraday point when I checked the signal; the final KRX close on July 31 was KRW 1.718 million. Chart supplied by the author.
The script only applies price data to conditions I defined. It does not understand wars, policy changes, distorted flows, or the fear people may feel tomorrow. An indicator built for crypto producing dramatic signals in Korean equities tells me less that it “works here too” and more that this market has begun to move like crypto.
The green triangle carries no responsibility. When it is wrong, it quietly moves on to the next candle. My account is the only system that reliably files the incident report.
The honest regret of someone who did not buy SK hynix
I did not invest in SK hynix last year. Pretending that its upper-limit close left me completely unmoved would be dishonest. This indicator has made me laugh and cry, but missing SK hynix belongs firmly in the second category. The stock hit its upper limit while my position remained impressively stable at zero shares. That was not the stability I had hoped for.
Regret, however, is not a current investment thesis. There is a large logical gap between “I should have bought then” and “therefore I should buy now.” A missed gain can feel like a loss, but chasing that feeling can produce a very real loss of a different kind.
This signal may later look like a remarkably accurate bottom, or it may become one more mark that failed to explain a violent rebound. I cannot know today. Refusing to cover that uncertainty with the color of an indicator is the minimum honesty I owe my own record.
The boundaries I wrote down again
I will not discard the indicator. Its value is not that it is always right, but that it records the moments when my attention and emotions change. I do not want to act on it unless I can answer four questions alongside it.
- Can I explain the reason for entering in one sentence?
- Have I defined the price or condition that would prove me wrong?
- Am I rushing only because I fear missing another rise?
- Is the size within a loss I can actually absorb?
A signal is a starting point, not an approval button. The day after an upper-limit move, the urge to chase can execute faster than analysis. In software I appreciate automation; in investing I prefer to leave a deliberate human confirmation step.
Time will tell whether the KOSPI and KOSDAQ rebound begins a recovery or merely reverses an excessive fall. The new buy mark on my indicator deserves the same uncertainty. All I know today is that the market moved violently enough to wake both my greed and my regret.
This time I am writing before I conclude. I executed the record before the trade. At least that order has a low rejection rate.
