You can pre-register for airport quarantine procedures via My SOS application on your smartphone.
With this app, you can complete some quarantine procedures before you enter Japan.
For more detail, please check the below website.
As part of border measures to prevent the spread of the novel coronavirus (COVID-19), enhanced quarantine procedures are in place for entry to Japan.
The quarantine measures that apply to you depend on where you stayed before entering Japan and whether or not you have received a third vaccine dose.
Please check which quarantine measures apply to you with the website below.