Plan

Here is your revised passage with improvements in grammar, clarity, and sentence flow:

Reeva sat in the chair, staring off into the distance. He hadn't expected things to escalate this far. When he first escaped to Tumidus, all he wanted was to build his business, make his money, and live happily as he always had. But now, it felt like it would be a disservice to himself and the world to let the white demon roam freely.

In the original story, nothing like this happened. Since he gained [Foreight], the white demon's existence had puzzled him. Why was there such a creature here when, in the original, it would have been a major plot hole not to mention it?

The only big difference Reeva could identify was his own presence. But that didn't explain why all of this was happening. If there was no white demon in the original, then something must have stopped it.