You can customize your translation settings: https://support.mozilla.org/en-US/kb/website-translation#w_customize-translation-settings

Sorry @wxie but this does not solve my problem. I want to have language to translate INTO to be preset. Instead the settings allow to set languages FROM which it will always be translated. So I will still have to scroll the settings to choose English each time I want to translate a page. Also, some websites have mixed languages and current firefox translation function doesn't always recognise the main language correctly, and will see it as English page.

Hi,

I believe Firefox pulls target languages from your device languages. Don't you have Japanese there?

Also, could you please share a couple of links to the affected websites?