Japan is in a unique demographic situation with over 27% at age 65 or above and 33% at age 60 or older. This elder population will have issues with health care needs as they continue toward longer life spans. Plus there are low reproductive rates for the younger people. The country of Japan needs to consider other options for their future growth and economic expansion.
Japan must open its borders to more immigration in order to foster economic growth. The country has been in a decades long decline due to an aging population that requires greater social welfare spending. Increased immigration would grow the country's population, while spurring economic growth. This would help the country deal with its aging population problem.
In theory, it makes sense to open the borders to increase the labor force. But the truth is, Japanese people are not going to be happy about that. I don't think they want to dilute their culture or open up to other cultures, even if it means losing their economic advantages in the years to come.
Japan does not need to open its borders to foster economic growth, as people aged 65 and over still spend their money as part of the economy, and need things like medical supplies that keep companies open. They may have to train more young people in skilled jobs, but don't need to open up.