Using Japanese characters in DOMPDF? - dompdf

Question

I'm trying to get my PDF's created using DOMpdf to work correctly with Japanese characters. I have it working fine with French etc, but Japanese characters don't show (just get ???)
Here is how the HTML page looks:
...but the PDF comes out as:
The code I'm using is pretty simple:
<?php
// include autoloader
require_once '/path/to/admin/invoices/autoload.inc.php';
define("DOMPDF_ENABLE_REMOTE", true);
define("DOMPDF_UNICODE_ENABLED", true);
// reference the Dompdf namespace
use Dompdf\Dompdf;
$order_id = $argv[1];
$content = file_get_contents("/path/to/admin/invoices/html_versions/$order_id.html");
// // instantiate and use the dompdf class
$dompdf = new Dompdf();
$dompdf->loadHtml($content);
// Render the HTML as PDF
$dompdf->render();
// Output the generated PDF to Browser
$dompdf->stream();
?>
From what I can see, it wants a font specifically for Japanese.
What font would work?
Can I have it running alongside the normal font? i.e I still want to be able to show stuff like íóé etc
UPDATE: I'm getting a bit closer!
I've downloaded the CyberCJK TTF font (as suggested here: https://github.com/dompdf/dompdf/issues/938 )
Then I tweaked my CSS to:
#font-face {
font-family: CyberCJK;
font-style: normal;
font-weight: normal;
src: url("https://example.com/cgi-bin/admin/invoices/lib/fonts/DejaVuSerif.ttf") format("truetype");
}
* {
font-family: 'CyberCJK', sans-serif;
}
#page { margin: 0px; } body { margin: 0px; }
html { font-size: 14px/1; font-family: 'CyberCJK', sans-serif; overflow: auto; }
..and now I get partial characters:
I have also tested uploading my HTML page on: http://www.htm2pdf.co.uk , and it comes out perfectly as a PDF, and is also only 64kb, compared to 13mb+ using DOMPdf. Something must be up!
I'm really at a loss as to what else to try :/