Note: @sosukesuzuki and @Naturalclar will help me with this PR so they will add some random commits to my fork repository, but that is intended.

@Naturalclar Are you already working on stage3.yml?

@sosukesuzuki Not at the moment, feel free to take it 👍

Amazing, thank you. I am unable to ok the content, can someone send me a ping when this has the all clear? I don't know if everyone has the right privileges. Let me know if anything is needed.

@rkirsling may be able to review Japanese content. If privilege means the privilege to merge this PR, then probably no one here has it except you. Of course, I will ping you when we make sure that we can merge.

For stage3.yml, I think it would be better to translate only the description section. What do you think? For example, "Top-level await" will lose its meaning when translated.

I rebased to the latest master.

@codehag By the way, the URLs for .at() and Import Assertions are wrong and seem to be broken.

@sosukesuzuki Would you still like to tackle this? (This isn't a huge rush btw, but just want to check.)

Yes. Sorry for delay. I'll create PR today.

All right, thanks! No need to apologize :) (Consider your contributions to us as much appreciated, but certainly not demands. Guard your own time carefully.)

I think this is already in a mergeable state. The final quality of this is very good, and if no minor problems are found, we can merge this.

Thanks to everyone who helped me with this PR. I probably couldn't have done such a high-quality translation without your help. (Actually, I'm not very good at Japanese.) And @codehag, this is finally really mergeable. Please merge this when you have time.

Thank you everyone!