In this use case, there is no designed homepage in German or in Japanese. The localized labels have a German translation, but no Japanese equivalent.
If a user selects Japanese as the UI language, the homepage defaults to the fallback language.
If a user selects German as the UI language, the homepage defaults to the fallback language, but the localized labels are in German.
If a user selects German as the UI language, all the custom pages are accessible, and all localized labels are in German.
If a user selects Japanese as the UI language, all the custom pages are accessible and default to the fallback language.