What should I do if my second marriage visa with a Korean is rejected?

If you want to leave at once, there is only one way, and you can go to an immigration lawyer to file a lawsuit.

But you have to weigh whether the benefits of immigration are worth it compared with the cost of litigation.

If you think it's too expensive to go to court, you can wait for a few years to have children before applying. Then the visa officer will no longer doubt the authenticity of your marriage.