Why are there fewer illegal immigrants in Japan?

After reading your situation, I think the main reason for refusing the visa is that the deposit certificate is not done well.

You can't travel (and study abroad) just by depositing your money a few days before you hand in your deposit certificate.

Is very dangerous. As an exchange student, you can't earn much money if you don't work in Korea for a long time.

At least that's what the Japanese embassy thinks. It depends on your capital, mainly on your deposit in the bank account.

If you don't have a lot of long-term deposits in your bank account, especially in the near future, that's a disadvantage.

And a few days before you submitted the deposit certificate to the embassy (it is estimated that you checked the income and expenditure of your bank account), your account suddenly increased by 800 dollars, about 5,000 RMB. The embassy thinks that the origin of your dollars is unknown, and the suspicion of fraud is well-founded and taken for granted. This should be the main reason.

There should be another secondary reason. You are an exchange student, and the time left on your visa may not be long. If it is easier to study in Europe and America, and the Japanese think that studying in Korea is inferior to them, and you have friends in Japan, plus you are considered to have problems with your savings, you will be considered suspected of having friends in Japan to help immigrants work.

It should be the above two reasons.