>>281962392
I'm looking at Japanese sources and comments and I'm not seeing much if anything about it being five acts. Japanese fans were predicting three or maybe four (based on a different structure type) acts since early on in the arc.
Here's a Japanese post about the end of Act 2 questioning how many acts there would be. Two replies mention 序破急.
http://animesoku.com/archives/19948132.html
The first correctly predicts Act 3 would be the last one. The second is in disbelief that the arc could end with one more act.

So where the hell did "5 acts" come from? How does that even make sense when the whole point is that it's a three act structure?
Actually, the main source for the five acts thing looks to be an English wikipedia article that cites a book written by a westerner. The book supposedly has a section referencing a Japanese playwright's book, but the part of the page that's supposed to link to that original book links to something shrine roads instead. The whole part of that article is evidently not very well written.