Okay, what is going on here. Is that maybe my favorite one-off Kamen Rider story? Let me check my list of criteria:
"Make sure ending is sad"
Oh okay. Yeah, that was hella good. What is it with Toei's ability to make such really good small stories while making such heartless, unfun movies? I'm guessing there's an expectation that the movies have to be 50 fucking Riders mashed against Shocker or Space Shocker or whatever again.
But no, this is much better. Sure, it is a bit derivative of Edge of Tomorrow/Groundhog's Day (Both highly recommended if you haven't seen them) but it was a good story that had a lot of great moments. Let me pause to talk about what's good about the movie on its own merits.
Yongou has a cool suit. The airman uniform is a nice variation.
Time is a great song. I loved it each time it played at the end of a segment.
It made good use of its materials. Let's face it, Takumi did almost nothing in the Sangou movie. But when reduced to a small group of people, everyone feels important. Even Kiriko acts as a diversion from the truth (I totally guessed it was Takumi by the way, as soon Kaidou showed up, it was obvious). The plot kept advancing with each cycle, it was just good and tight.
Oh yeah, no idea what was going on with the Shocker Great Leader. Someone's been watching too much The Prisoner.
So what elevates this to being tremendous? How about fucking Kaidou is back. Karahashi Mitsuru is a lovely man and he's guest starred on a lot of things that benefited from his charm, but going back to his roots as Kaidou? And then having him interact with Takumi? Oh, so good.
What else? Toei must have spent 10 years regretting the ending to Faiz, since they keep coming up with ways to improve upon it. If Kamen Rider Taisen was the proper epilogue to 555, then this is the true ending that you get for suffering through all the side missions. It's a proper ass ending to Faiz, and it matches with my theory that Takumi dies at the end of the series. I mean, I honestly don't care either way, but you guys know I love to be right.
And Sangou's ending was a bit dumbed down. Yeah, Sangou erases himself from history, but the guy's still alive and doing race car stuff somewhere. Takumi destroys the machine knowing that he's erasing himself from history. Not even a memory, not even a damn photo of his existence are left in the memory of his friends. I hate 555 as a TV series, but what a brilliant way to take a horrible sloppy plot and turn it into some beautiful. This and Kamen Rider Taisen has shown that Faiz is a true Rider.
Edit:
Summary for 555's ending:
Spoiler
The problem is that 555 ends on a notoriously unsatisfying note. It's hinted that all Orphenoch will eventually die soon, except that maybe the King survived, and he might have made one of the villains live forever and she gets off scott free. One villain reforms and decides to live as a human. One good Orphenoch, Kaidou, also decides to go off and live among the humans. And Takumi's ending is more or less what you saw. It's ambiguous whether or not he dies at the end, but I like saying it does, since it's already pushing fans who are sour on the ending for other reasons.