Problem changing languages in Win 10, with a twist

So a while ago I went and changed my laptop's region to be able to install a Japanese VN (visual novel). Everything worked just fine, nothing out of the ordinary.

So yesterday night I decided that since I wasn't really in need of it I would change the region back, so I went and did so. Big was my surprise when upon restarting my laptop wasn't only not in my native language (Spanish), but it was all in Japanese! I went and followed the million tutorials on internet to no avail, when I realized that there is something that's probably different.

Every time I turn my laptop on I get this picture:



Suffice to say, I have no idea of what it says, but I'm guessing this is what's keeping me from changing things back to normal.

Any ideas of what the hell it says and how to solve this?

"there's a possibility that cannot access this disk is broken. please make sure whether it is a disk with a recognizable format in Windows, you must be formatted before use"

Which doesn't really say anything to me other than I broke something, somehow.