On March 26, 2020, the Japanese Government decided to apply a new border policy to Japan immigration from Vietnam. This measure has been applied since March 28, 2020.. It is recommended that those who plan to come back to Japan or travel Japan should note this provision.
On March 26, 2020, the Government of Japan held a meeting of the Steering Committee for COVID-19 Prevention Policy and decided to apply the following new Japan immigration measure to Vietnamese.
People who enter Japan from Vietnam are requested to spend 14 days at the location designated by the head of the quarantine agency (it is currently assumed that they will stay at their residence for 14 days). And, they are not permitted to use public transportation in Japan.
The requirement is effective from 00:00 28 March 2020 till the end of April 2020, applied to those traveling to Japan by plane or ships. The provision deadline may be extended.
Terms (1) and (3) as mentioned above are effective from 00:00 28 March 2020 và extended to the end of April 2020. The deadline may be extended.
Link source - Embassy of Japan
https://www.vn.emb-japan.go.jp/itpr_ja/thongbaonhapcanhnhatbanlienquandenvirutcoronathemoi.html