That's bizarre. Potentially a corrupted file. I would download the whole thing and extract it again. Then just click the Game.exe to play.
Doesn't need any installing really.
I fixed my issue as far as the game's installation is concerned! Now I'm stuck on not being able to complete the "Shiny Monstrosities" side quest
I'm glad! That's just the area where the tanks are in Toko City.
Once your big enough, you can barge your way through and then explore the facility. Once you beat the "boss" there, you can complete the quest.
