Ending's Logic

First, refer to Wiki: Predestination Paradox to understand the relationship of Blick Winkel, You'haru's plan, and the entire 2034 incident.  Blick Winkel lives through the artificial accident of 2034, gaining knowledge of the plan and his own existence, confronts You'haru.  You'haru tells Blick Winkel to travel through time and save Takeshi.  Blick Winkel does so by first telling the 2017 You'haru, who just got rescued, that Takeshi and Coco were left behind.  Traveling back to 2034, Blick Winkel finds supposedly happy-ending world falls apart.  The reason is: if Takeshi and Coco were saved in 2017, everything in 2034 would not happen, and consequently BW would not appear, awaken, and go back in time and save Takeshi and Coco.  Having figure this out, Blick Winkel then goes to the 2017 You'haru, tells her to recreate the condition in 2034 to trick himself, shall then it will be summoned.  You'haru listens and carried out the plan faithfully, and with the involvement of Blick Winkel, causality is violated, but everyone gets to live after 2034.

According to the popular Parallel Universes theory, the world which Takeshi and Coco got immediately saved will not fall apart.  The reason why it fell apart is, it couldn't exist in the first place.  Notice BW expected to see everyone on Insel Null of 2034 after the initial attempt.  If Takeshi is saved, Hokuto and Sara will not be separated from their parents, LeMU probably would not be rebuilt, Leiblich probably would be taken down by government right then, and nobody has any reason to gather on Insel Null on May 7th, 2034.

Why is this happening?  Remember Hokuto's conscious is with BW as it travels back and forth in time. In a relatively short period of time, Hokuto's way of thinking probably influenced Blick Winkel, the 4D being, from looking at the big picture as we expect a 4D being would do.  (after all, a normal 4D being has no reason to change history of our 3D world.)  Hokuto's way of thinking is just what how we think.  Would you really prefer a world that changed so much? Would you want to see a whole set of different history after 2017?  Would you want to see 2034 You'haru's effort without reward since her world no longer exist? (ok, forgot to mention, it seems that the world only exists when BW observes it, something you'd seen in a quantum novel).  Blick Winkel makes a humane choice of preserve everything--even Hokuto and Sara's painful childhood, Tsugumi's 17 years of agony, You'haru's sinful deceit to her clone.  What would they choose?  It is their memory, even though undesirable, but it still is part of their existence.  This is not Butterfly Effect the movie, there is one not perfect but good-enough ending for everybody in Ever 17, it is what you have achieved.

One thing that was troubling me: seemingly incompatible theory of Predestination and Parallel Universes both appear to be incorporated into the story.  In the Parallel Universe, every timespace is purely branched off from a choice, or by chance, where infinite number of timespaces exist.  When you look at the Predestination theory, causality is violated, the effect becomes the cause, and vise versa.  I'll call the final ending a "humane resolution", which the script writers bend logic with emotions.