Downloding Win10_2004_Korean_X64.iso from Microsoft directly with safari, or techbench => both are too slow, about 10~30kB/s.
https://www.microsoft.com/ko-kr/software-download/windows10ISO
https://tb.rg-adguard.net/public.php

I searched in Naver.com about this issue and found a private site with link to Google drive file download:
https://m.blog.naver.com/hankboy/221116251847

I will also download Win10_2004_Korean_X64.iso from Microsoft to compare the files later.