@javier_the_stupid_asshole
This is a folder/hard drive writing permissions error.
Usually, when this happens it's because the folder/location you're running the game from doesn't have the correct folder permissions such as "Administrator access"
Or because another program is blocking the game folder from creating the temp files needed to play the game such as an anti-virus program.
A couple of suggestions :
1. Move the game folder to your desktop and run it. <- "This fixes a lot of issues with running RPGMV games"
2. Depending on which Anti-virus program you're using you could disable it for a couple of moments and try running the game to see if this is what is causing the issue.