Detective Precure Episode 31 "Detective Cure Arcana" Impressions (※Caution) Spoilers Included

First, I'll place a cushion. This contains spoilers and personal impressions, so players who don't want to see it, please turn back. Including this episode and the previous one, "Eclipse Shadow," I'm filled with the feeling of "No way that would happen." First, the Great Demon King's prophecy comes from a mysterious item called the "Mirage Book." I can understand that. But fundamentally, I'm thinking, "What is the 'Mirage Book'?" and since I can't trust it in the first place, if we assume Ruruka is going berserk based on it and look at it, it just looks like a red herring. Including this episode, episodes 30 and 31 have left me constantly thinking "???". Dechi Again is very flustered and only says cryptic things, which makes it even harder to understand. From the name itself, it sounds like "fabrication," and hearing the new ending where the mystery isn't a mystery, I end up thinking, "So, you're the culprit?" Given how high the quality of the story has been up to this point, I ended up feeling "Hmm..." Since Ruruka has been going berserk with the Mirage Book the whole time, I even think that if it were gone, the problem would be solved. What do you all think? I personally don't like stories about individual rampages, so it was complicated.