What this site is, who publishes it, and how to catch it being wrong

Written for a ten-to-thirty year clock

Long Horizon is for one kind of reader: someone who intends to own businesses for a decade or more, and who lives in the United States, Japan or Korea. Nearly all investing content is written to a much shorter clock — what moved this quarter, what to buy this month. Very little is written for someone whose next real decision matters in twenty years.

Three things follow from that, and they shape every page:

• Structure, not tickers. Companies appear here to explain how something works — how an index is built, why a sector consolidates, what a multiple does to a return — or as case studies of something that has already happened. They do not appear as suggestions.
• The principles are the same in all three countries; the accounts and the taxes are not. Compounding, diversification and behaviour do not change at a border. Which account to use, what gets withheld and what you owe in May all do.
• Nothing is timed. A page that would be embarrassing in six months is a page this site should not have published.

A student in Tokyo, from Seoul, with no financial qualification

I am a university student from Seoul, living in Tokyo. I read and write Japanese, English and Korean. I do not work in finance and I hold no financial qualification of any kind.

I found investing during the pandemic, through a Peter Lynch book. That sent me off to research US, Korean and Japanese companies on my own, and eventually to the conclusion that long-term index investing suits me better than picking individual ones. Because I started in 2020, I went through 2022 rather than reading about it afterwards.

This site exists because what I was learning kept piling up in scattered notes. Japan's NISA, Korea's ISA, America's 401(k) and IRA are all relevant to me, and yet almost nowhere in any of the three languages explains them side by side. The comparison notes I made for myself became this site.

The three markets are not an arbitrary selection. They are the United States and the two Asian countries most closely bound to it, in security and in trade — a relationship I am assuming holds for decades, which is the same horizon the rest of this site is written to. They are also the three I have a personal connection to and actually follow.

Long Horizon and Tokyo Kuroishi are the same thing under two names

Long Horizon is the name of the publication — the title at the top of every page. Tokyo Kuroishi is the GitHub account that publishes it; the site is served directly from that account's public repository, which is why the address is tokyokuroishi.github.io. One is the masthead, the other is the account it is hosted under. There is no company, no team and no organisation behind either.

Five rules that delete paragraphs

These are not aspirations. They are the rules that get text cut before it is published.

1. No forecasts for individual companies. No price targets, no "this one will win". Where a company is named, it is explaining a mechanism or illustrating something that already happened.
2. No buy lists. No recommended portfolios, no "best funds for 2026", no rankings. The site has no idea what suits your situation and will not pretend otherwise.
3. No invented numbers. A figure that cannot be traced to a primary source is either labelled clearly as an assumption or removed. This is the rule that costs the most words.
4. Assumptions are labelled as assumptions. The 7% in the calculator is a number you chose; it is not a prediction, and every result built on it says so next to the result.
5. Nothing is ever ordered by what pays. See Money below.

How errors are handled — and why you can check that they were

This site will get things wrong. Tax rules change without the page noticing, companies get taken over, and a sentence that was true in March can be false in September.

• Factual errors are fixed on the page itself, not buried in an appendix, so nobody arriving later reads the wrong version.
• Every section carrying institutional facts shows the date it was last checked against its sources. If that date is old, treat the figures as old — the site does not update itself.
• A correction that changes what a paragraph means is kept visible rather than silently overwritten, because the point of a dated record is lost if the record is edited.

Drafted with AI assistance, and why you are being told

The pages on this site are drafted with the help of an AI assistant and reviewed before publication. That is disclosed here because it should change how you read them: an AI-drafted paragraph can be fluent and confidently wrong at the same time, and a plausible sentence is exactly the kind of error that survives proofreading.

Rule 3 above and the source blocks throughout the site exist because of this, not despite it. Every regulated figure is checked against the body that publishes it and stamped with the date. Where a claim could not be confirmed against a primary source, the site says so in place rather than stating it flatly — there are such notes on the Korean accounts section, for instance.

How this site is funded: currently, it is not

As of the date at the foot of this page, Long Horizon carries no advertising, no affiliate links, no sponsorship and no paid content, and collects no payment of any kind. There is nothing to disclose because there is nothing there. What the site does and does not collect from your browser is set out on the Privacy page.

If that ever changes, it will change visibly:

• Any affiliate link is marked with a visible badge at the link itself, and a disclosure notice appears automatically in that section. The notice is generated from the links on the page, so it cannot claim a relationship that does not exist, and cannot go missing when one does.
• The editorial rule that governs it: only link to something the page would have recommended anyway, and never reorder, promote or soften anything because of what it pays. A commercial arrangement that changes a sentence forfeits the only thing this site has.

What this site is not

Personalised investment advice for a fee is a licensed activity in all three markets this site covers:

• Japan — 投資助言・代理業 registration under 金融商品取引法.
• Korea — 유사투자자문업 obligations under 자본시장법.
• United States — investment adviser registration.

Long Horizon holds none of these registrations and does not seek to. It publishes general education and tools, which sit outside them. It cannot tell you what to buy, what to sell, or what is right for your circumstances — and if a page ever appears to be doing so, that is a defect. Please report it using the link below.

This page last updated: 12 September 2026.