Demonized can be bought at the shop at any time for 2,000 coins. If you need more coins, try playing Faces of Killed 3. You get 10 coins per kill, and they add up quickly. I will include a section of the guide from ManicMetalhead
below, with more info about Faces of Killed 3:
From the Main Menu, look at the Movie Shelf and highlight the movie called 'Faces of Killed 3' (it's on the third row down). It may also be called 'Yo! Skullface!' depending on your game settings.
You'll be thrown into a mini-game (which is a good place to make some money as well, coincidentally) that is all based on your reaction times and a small dose of luck. You'll see a bar appear at the bottom and a segment of that bar will show up red. You simply have to press when the arrow slight above the bar is over the red section.
Doing it once, will count as 1 in the chain, and you'll see a gory kill in the background (unless you're on PG settings).