Japanese Tax on US Capital Gains from Stock

I'm a permanent resident of Japan. On my Japanese tax return for this year, I will have to report capital gains from the sale of some US stock. All I can find online is information saying that capital gains from the sale of overseas stock is reported "separately from ordinary income" in Japan and is also subject to "separate taxation". Fair enough. I called the National Tax Agency information hotline for advice, but they were of no help.
Does anyone know about this (eg: Which Japanese tax form(s) to use? What the tax rate is for capital gains on overseas stock? etc.)
Later, I'll probably end up going to a Japanese tax professional for help, but in the meantime I want to try to understand what I'm up against, and also try to learn the related vocabulary in Japanese.

as same as domestic stock selling.
national tax : 15％申告分離課税
residential tax : 5 %
分離課税 : the tax will be calculated separately from your salary.
you may choose 総合課税 (combine your salary and capital gain). in mot cases, 分離課税 is better (cheaper tax).
calculation of capital gain : exchange at TTB on the selling date.
you can claim 外国税額控除, if US withdraws some tax when selling.
the system is complicated.
follow the advise by an accountant.
you can use the ordinary form. just fill the columns as same as domestic stock selling. (I believe)

Yes, that is exactly what I want to find out about... the so-called "separate taxation" (分離課税) of overseas capital gains.

Thanks, Ken!

I'm going to keep searching online for information about 分離課税 and about how to report overseas capital gains. I want to have the correct Japanese vocabulary and the "separate taxation" tax forms when I talk with an accountant and with the tax office people.

If anyone out there has links to specific sites with explanations -- in English or Japanese -- as well as a link to the exact Japanese tax form(s) to use, please post the links here.

Do you use Shinkokusho A?
I believe it will be Zatsu shotoku. There is an instruction on how to figure the amount.
You apply the amount to the Income column (shunyu) ㋒. You can deduct expenses from your gain and you put the deducted amount to the tax column in the shinkokusho A (shotoku kingaku �A.
I am not sure about which yen rate to use.
If you are American and you also file U.S. tax return, I am not sure about you file this gain with Japanese tax office because it will be double taxation. 　　

譲渡所得,jyouto-shotoku
https://biz.moneyforward.com/tax_return/basic/joutoshotoku-shinkoku/

necessary documents and forms
1.確定申告書B
https://www.nta.go.jp/tetsuzuki/shinkoku/shotoku/yoshiki01/shinkokusho...
2.分離課税用の申告書(第三表)
https://www.nta.go.jp/tetsuzuki/denshi-sonota/kokugai/yoshiki/pdf/02.p...
3.株式等に係る譲渡所得等の金額の計算明細書
you can make in any forms (for example, you can make it by Excel.)
buying: date, yen/USD rate, amount, handling fee, etc.
selling: date, yen/USD rate, amount, handling fee, etc.
if you convert between yen and USD when buying and selling, you can consider the exchange fees as necessary expense. generally, if you use TTS for buying (convert yen to USD), TTB for selling(convert USD to yen), your tax will become lower, if that is true. otherwise, use TTM.

I use Form B.

It seems that I'm supposed to use this version of Form B:
申告書B（第一表・第二表）・申告書第三表（分離課税用）

http://www.nta.go.jp/tetsuzuki/shinkoku/shotoku/kisairei2011/pdf/shink...

In the past, I asked the local tax office for help with my return, and they did not tell me about "separation taxation." So I paid too much tax by using the higher tax rate.

In addition to using the lower tax rate (15% national + 5% local) for this year's tax return, I want to look into amending some previous returns to get money back since I paid the higher rate (33% national + 10% local) in the past.