Hello 宏幸

I'm sorry, but I don't quite understand what's going on here.

You need to translate the template file as well if you need to send it out in Japanese, as the other text.

Otherwise, please explain what the issue here is in more detail.

Hello again 宏幸

This should work fine. Especially when some placeholders work fine, while others don't - that's a strange issue.

Please provide me a temporary WP-admin login for your site where this happens, so we could log in and take a look ‘from the inside’ as that’s the most efficient way to see and resolve the issue. We do not interfere with any data or anything else except for the plugin (in case that’s a production version of the site), and of course we do not provide login data to third party. You can write credentials here just check Private Reply so nobody can see them except us.

No worries, 宏幸 

I received an e-mail with the log-in credentials, but unfortunately I wasn't able to access it:

Can you please white list my IP Address 82.117.217.10 and country (Serbia), so I can remote in?

Hello again 宏幸

That worked, but unfortunately there's CAPTCHA in Japanese:

I cannot enter that, so can you please disable captcha so I can log in?