1.   .htaccess at root directory (e.g. norikoguide.pepper.jp/)

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /norikoshop/index.php [L]
</IfModule>

# END WordPress

is effective onWP at child directory (e.g. norikoguide.peppere.jp/en/)

Note!!  Rewrite Base /

Without this, you get Page 404 when changed other than default, although it says permalink strucure updated on the dashboard.