I find it interesting how Watashi's perspective of Ozu is essentially reversed once he bothers to look into Ozu's background. So much to the point where he no longer sees him as this insidious yokai who's out to ruin his life. That Ozu was a lot more romantically flawed, and that he wasn't nearly as insulated from any sort of retaliation for his deeds. Since Watashi wasn't privy to those elements of the story in those individual timelines, seeing all of it come together made him realize that Ozu wasn't kidding about being tied together by the "Black Thread of Fate". While Watashi was doomed to fulfill an unsatisfying campus life because of his uncompromising personality, Ozu had the much more potent threat of disappearing into a raging river as payment for all his mischief. Perhaps Ozu himself was aware that the both of them were stuck in the same fate. Perhaps the castella in every room was evidence of him keeping the hikkikomori version of Watashi alive long enough to overcome his own flaws, so that he could one day come out and save Ozu himself. This is all baseless conjecture, by the way.

Did you ever notice that all the narrator's films became their own alternate realities, and that his final unfinished film was essentially completed in the last episode? It doesn't hold a lot of meaning, but it's something I missed when I first went through the anime.