Game resized desktop resolution (zooms in a lot) and has borders all around in full screen? If so I had the same issue.

Open the game -> options -> turn fullscreen fetish off

at this point you should see a little of your desktop. Move your mouse above the game window, then lower it over the game window bar. The mouse cursor disappears, but right click anyway. 

Click properties -> Uncheck "Launch in fullscreen" -> Close and reopen the game (should be windowed, but normal now) -> options -> turn fullscreen fetish on for normal fullscreen without borders

The setting seems to be shared between some rpgmaker games, so if you check the box in another to make it fullscreen, you'll have to uncheck it again for lona. Pretty sure the setting automatically changes display resolution to 640x480 while the game is running, which is what causes the weird behavior and borders.

That patch of white seems to be the game window btw. If you move an always on top window (Like the magnifier tool) over it, it'll be gigantic and in the way when you go back to the game.