Firstly, your sister has to learn Japanese. Of course she can choose to study Japanese in Vietnam, but she has to gain her nursing qualification from a nursing school in Japan. So, I suggest that she comes to Japan and studies Japanese.

If she gains this qualification, she will have the potential to work in a Japanese hospital. Usually one would prepare for the nursing school examination while studying Japanese. As there are many nursing schools in Japan, you had better consult with her Japanese school.

If she passes a nursing school examination and obtains a qualification, she could work as a nurse at a medical institute in Japan. However, the longest period she can work for is four years under the current law, but it seems there is a possibility it will be eased in future due to Japan?s low birthrate and aging society.

Your sister will have to apply to change her visa status. The correct visa status for nurses is ?Medical.? She will need to submit her academic record, a certificate to prove her qualification, details about employer and the contract, etc. Her income has to be the same or more than Japanese.