I highly doubt that the government of Japan will allow the boxing match in Tokyo. As per https://covid19japan.com/, Tokyo has the highest cases of Covid-19, so it's not likely that they will simply go there as venue alternative.

Besides, I also don't think that Arum will allow that fight to happen in Japan, we all know how Arum works, its all about how big Top Rank can milk this fight. I guess it is Inoue statement alone and not representing Top Rank, perhaps he just blurted it out of frustration because he is eager to go fight the best version of Casimero at this point.