Can you spoiler-tag me what that is? I didn't watch the movie, so it got me curious.
Well, it is not exactly game changing but it is actually a cool detail when you consider the concept of Ultraman:
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See, one little detail that Nexus brushes off to the side in the first episodes is the naming of Ultraman; TLT and the Night Riders originally referred to him as the Silver Giant until Komon, our protagonist, named him Ultraman for reasons that even he cannot explain.
This seem like an unimportant detail... until you factor in the movie: after Ultraman defeats The First it is said during the prologue that peace returned and that the children named the giant who saved the city as 'Ultraman'.
Here´s where it gets clever, for one of the key plot point of Nexus is how the existence of the Space Beasts must remain a secret since it would create panic and the fear of the population could empower them. To ensure this TLT created the Memory Police, whose job is to erase the memories using the technology they got from The Visitors AKA the alien race who was previously destroyed by the Space Beasts, and one of their first jobs was deleting the events of Ultraman The Next from everyone´s memory, something that is revealed in the last episodes of nexus where the Night Riders discover the case files about the events of the movie and realize that there was a major conspiracy to hide everything.
This is the reason why Komon named the giant as Ultraman; though it is never explicitly said, Komon managed to vaguely remember the events of The Next, maybe because he was a deunamist, which is why he merely said that the name 'just popped up in his head' when he saw Ultraman.
Now, the memories that are deleted from people are not lost forever since they are actually stored inside Lethe, the sea of memory which is deep within the TLT base, and during the last episode Dark Zagi destroys Lethe in order to empower the Space beast with the fear of the population, and here is where the big twist comes up.
During the final battle between Komon/Ultraman and Dark Zagi, people start remembering not only the attacks of the space beasts but also how Ultraman saved them, and people actually start calling out for "Ultraman" because they remembered the silver giant that saved them 5 years ago.
This is what i find really clever; sealing the memories people had did prevented the Space Beasts from growing stronger since they could feed on fear, but this also weakened Ultraman since he is essentially powered by Hope, so when people started to remember how Ultraman saved them during the final battle, Komon managed to become Ultraman Noa because of the hope of the people who remembered the events of the Next.
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You don´t really need to know this to enjoy the series, but man, that is a really cool twist that ties to events of the movie with the series in a neat way.