mPDF Japanese font configuration

I need to generate a PDF using mPDF and YuGothM.ttc font for a Japanese client. The page I need to export in PDF contains some text which in browser version (HTML) is rendered well, but in the PDF, the same text has some characters using a font and other characters some default font which is not approved by the client. I understand I have to define TTCfontID parameter in every font definition for .ttc files, but I just don’t understand the meanings of those definitions and so how to properly configure fonts.