I have a little theory that a thing that makes Japanese website feel Japanese is their choice of typeface, which will almost always be something with robust CJK character support. This typeface is preserved when Chrome auto-translates the site.
But fonts with good CJK support have wider Latin letter-forms, even when not in `font-variant-east-asian: 'full-width'` mode. I write about this here: https://maxbo.me/subordinate-latin.html (and cite "the peculiar case of Japanese web design")
That's the fallback font when the font that is requested is not available locally (and the license doesn't permit them to be redistributed). I wanted it to be visually obvious.
But fonts with good CJK support have wider Latin letter-forms, even when not in `font-variant-east-asian: 'full-width'` mode. I write about this here: https://maxbo.me/subordinate-latin.html (and cite "the peculiar case of Japanese web design")