[Tsuwabuki]

It totally isn't that easy.

If you're already in Japan and you need to switch from a tourist visa, you're not even allowed to wait in the country for your COE. They won't send it to the company until they have given immigration dates certain you will be outside of Japan. If you're slick, you can manage to work the dates so the CoE arrives "at the company" around the same time you leave. Then you take it with you, hit Korea, come back. I had to do that. It was a serious hassle.

And they nearly didn't let me back into the country because while I had a work visa, now, I wasn't coming into the country with any baggage, which was a pretty strong point I had been residing in Japan on a tourist visa, which isn't illegal as long as you're not working, but Is Not The Intended Purpose of Your Visit. And Immigration can deny you entry for any reason they want.

Make sure your ducks are in a row.