Upvote:-1
When getting tested in the EU, you will normally get a EU Digital Covid Certificate, which is in itself a proof of test written in English, which means that outside of specific countries (Like China), is valid for entry in Japan
all the items must be written in English or Japanese
Upvote:1
I really don't think you need to worry about Poland at all. What would be enforced there is any Polish regulation. Back in January, this could be checked even on a layover but as far as I can tell there is no test requirement at the moment. This also matches my recent experience of intra-Schengen/intra-EU travel. Even when a vaccine certificate is technically required, enforcement has been non-existent.
What does matter however are the requirements to enter Japan. They can be enforced at two points:
For both, a certificate is typically required (that's what they are for, really) but I have no idea how this is handled in Japan.