Long term capital gains tax questions

I see on the tax declaration guide that I can get taxed lower for stocks kept for more than 5 years.

What happens if I am buying more of a fund every month for 10 years, and then start selling? For tax purpose, would it be better to start buying a different similar fund 5 years before I plan to start withdrawing to make sure I can withdraw my savings at the lower tax rate?

What proof do I need to submit that the shares I sold were purchased over 5 years ago? Especially some shares I bought 4 years ago and grew 500% are on a foreign brokerage, and they don't provide history over 2 years old. So the only proof I have is that I owned those shares in January 2024. I'll try to contact the broker, but I'd like to know my options if they can't certify when was my last purchase for the stock.

Also, how would they know I didn't sell and buy again in that 5 years period? It's not my case, but just curious about that.

=> UPDATE: so as told below, stocks don't have that fancy short-term/long-term thing. That's good news.

now the issue is that by regularly buying stocks in my home country, I was supposed to somehow record the cost average in YEN, and the fund I was buying in got erased and fused into another, with a different price difference. I have no idea how I am expected to handle that.

Also anyone understand what page 3 is? I know that it's last year guide I'm looking, but I'm trying to get ready here :/

Please note that capital gains from transfer of land, leasehold rights, or capital gains from transfer of shares are subject to separate self-assessment taxation (see page 10). In this case, fill out the Page 3 (separate taxation form) etc. in addition to Page 1 and 2.
* Amount of income shall be calculated by the “Statement of capital gains (appendix to a final return form) [for aggregate taxation] [譲渡所得の内訳書(確定申告書付表)[譲渡所得] ]”, and submitted with the final return.

The 譲渡所得の内訳書(確定申告書付表) has several documents on the NTA website, but none match the [譲渡所得] , even googling it directly.

by sebjapon