Final Life: Cursed Soul Windows game

This started out as a book when I was 14. Now it's being turned into a game because the book was wrote just like a video game. Summary: Four young boys destined to save the world from a evil demon. They are descendants of the Fallen Heroes. The Fallen Heroes tried to fight this demon but failed to slay him, with the last of their strength they sealed the evil away. 200 years later he has broken free and still is determined to take over the world. Using his corrupted black soul, he will absorb mankind's pure green souls. These four boys don't know about their destiny, nor do they know of their ancestors. They live a normal day everyday, guarding miners in the mine from monsters. But this day will be different, things are about to change for them and not for the best.