Here are the latest guidelines from the Ministry of Justice / immigration, Japan. All those having residence in Japan, including students, are now allowed to enter Japan. First timers, not having residence in Japan, will not be allowed to enter yet. I think such people will be allowed in next phase.
Life in Japan
JA Passengers can have their baggage collected from their lodging in Japan, in advance, and delivered to the airport. To retrieve baggage, please go to the counter on the international departure floor in Terminal 1 or Terminal 2.
For the first time to visit Japan, you may be in trouble with buying groceries at supermarkets. This following table may help you how to explain what you want to buy in Japanese.
NHK Japan have some useful resources to help you learn Japanese
In preparation for a large-scale disaster occurring in the Tokyo metropolitan area, we used the visually appealing and memorable medium of anime to make a "disaster prevention educational video" with the objective of conveying easy-to-understand disaster-prevention knowledge to foreign residents of Japan