Did not pay attention to it being a translation at first which is a shame since I cant share inputs that might give some ispiration, still going to though.. I really enjoy the direction of the fanfiction but would probably like some way of incorporationg the fact that demons and evil spirits have always been around in "canon". Lets just say for example that general wizard population is unaware because it would be dealt with in their society by unspeacables who wipes and alters memories of the magicals so that their population dont believe in god because of the bad blood between them (witch hunts and all that).
Muggle society has priests who deal with possessions and the like within their limits, any deaths and strangeness are covered up by the DOM so that people wont notice the strange and unnatural deaths which would eventually lead to more muggles praying to a higher power for protection. This would be the wizarding society's revenge against god, having made a much smaller part of society believe in god over a long period of time to weaken said god and eventually kill them when not enough people believes in them.
I have fun imagining what directions fanfictions could go, I usually do not share my own opinions because I do not want to potentionally ruin the planned story of the author, by allowning them to take ideas that they do not like in the future and cause them to lose motivation to write because of the messed up story. But since this is a TL I see no harm in sharing my own thoughts that seemed fun in my head but would be hard to implement without plotholes ^^