I found it very frustrating you cannot buy paracetamol in Japan. I wonder if the know something we don’t…
http://www.survivingnjapan.com/2011/01/how-to-find-tylenol-i...
It's heavily advertised and available in every drug store in Japan (you don't even need to go to pharmacies!).
https://www.tylenol.jp/products-tylenol
If you were hunting for paracetamol during the pandemic, it could be that it was all sold out because it has been recommended as the medicine to counter COVID-19 symptoms and if there is anything I trust people in Japan to do it is to be able to stock up on things at a time of emergencies.