How to Enter Japan - TOCAT9 (catsj.jp)
Good News!
MOFA (Ministry of Foreign Affairs of Japan) updated information about entering into Japan. Self-quarantine period and place of accommodation after entry into Japan willbe changed according to the grouping ("Red", "Yellow" and "Blue" categories) of the countries/regions from June 1st, 2022.
Group "Yellow": On-arrival test and 7-day home quarantine (or 3-day home quarantine + negative result of a voluntary test) are required, however, those who obtain a valid vaccination certificate are not required to have on-arrival test, home quarantine and other measures.
Group "Blue": Regardless of the vaccination status of the entrants/returnees, on-arrival test, home quarantine and other measures are not required.
<UPDATE (as of May 27, 2022)> Grouping of the countries/regions has been announced.
You can check your country/region: Border measures to prevent the spread of novel coronavirus (COVID-19) | Ministry of Foreign Affairs of Japan (mofa.go.jp)