I'm posting this guide because after talking with someone who has finished The House in Fata Morgana, I've noticed that there's a few people who missed important things during the fourth door.
I'm talking about the text in the backlog that consists of new lines, hidden conversations between two characters, and censorship of already seen text.
You can easily understand that if you missed this during your first run, uncovering the truth about the fourth door's existence and the truth about who You are to be able to reclaim Yourself might seem to be a little far-fetched. This guide is for those who missed this.

If you have a save file from the fourth door or have already finished the game and it's still installed, you do not need to read this guide. You just have to check the backlog during the fourth door.
For anyone else who is past this point and doesn't want to go back or reinstall the game, I'm posting the following screenshots in chronological order.

The following are spoilers!!
I'm not putting the images under a spoiler tag otherwise it would be a little tricky to hover over all of them.
Also, I'm not posting them in the screenshots section since spoiler tags expire after four weeks there.

If you prefer you can see the screenshots in their imgur album[imgur.com]. They're all in chronological order.

Most of the conversations that we have already read between Michel and the White-Haired Girl are censored out.
You can read the ominous messages that are from ???, while all the confused sentences are from ???, and also a new conversation between the two that never showed onscreen appears.
These do not appear anywhere else except in the backlog.

Above I have posted only the screenshots that include the added content but not the whole censored conversations between Michel and the White-Haired Girl, because that's almost the whole door and is of no help to us.

An example of the censored text.


The censored letters and later entire words are of no particular meaning when put together, but if you want a couple of examples here you are:

dark close friend mine
dislike sun
light strong me
unholy monster exposed sunlight aything unholy
My name you
than me

looking for a while
you're empty man
the witch
believe witch's legend
I
accusations witch
area welcoming outsiders
especially stands out
you region
stay heard
I cast house
poor family
barely everyone fed
weak I am natural I to go

Apart from what the Man in the Painting says to You during the Investigation chapter, the Maid's memories that clearly show inconsistencies at times, and the censored text, there are other hints in-game to show that this door is indeed a fabrication, like the "glitches" that happen more than once during this chapter:

Last time I checked, only this door has hidden messages.

If you are playing a version in another another language and want to show your screenshots in another guide, please feel free to do so.

Thank you for reading!