If you were Sento, how would you feel about Build’s ending? (MAJOR SPOILER)
 

This is HYPOTHETICAL question! Since this is spoiler-heavy post, get out of this post if you haven’t watch the entire Kamen Rider Build.

Just says you defeat Evolto as your world is about to combine with another world, you woke up in a glass and you realizes you are in a new world.

You save the world but at the cost of everyone including Misora, Sawa, Gentoku, Kazumi and people you know no longer remember you as they are basically new timeline version of your old friends.

So now how would you feel that even though you save the world, everyone you know don’t remember you and you & Banjo are on your own?

Uh, if I'm Sento and the Build series just concluded, that means I also just wrote all of the Kamen Rider Build TV series, which is excellent. I guess I'd feel pretty good!

Even though many people except your Banjo you knew doesn’t remember you, you still okay with it?

I mean, I was mostly joking (Build's a great TV show but it's probably not the best thing Sento will do with his genius), but, yeah, I think I'd feel good about it.

Sento's a hero, and I think he sees all of his friends being happy and knows he did the right thing. It's bittersweet, for sure, but he saved two worlds and all of his friends. He's still got Banjou, and that's a loss he'd probably have a tougher time being okay with.

Also, every single one of his friends gets their memories back about ten minutes into the Cross-Z movie, so there's light at the end of the tunnel.

(Seriously, though, dude wrote all of Build. How could he not be pleased with himself?)

Didn't the post movie films establish everyone who was infected with the Nebula Gas regained their memories?
So Sento's circle of friends all remember him, now?

And I don't see why Sento wouldn't be proud. He can first of all be his own man (No longer being tied to Takumi, although his resemblance to Sato might be annoying), and he can rest knowing that he rebuilt the lives of those who needed it.

This doesn't answer your question, but now I'm just imagining how fun it could be to have a Kamen Rider series where our viewpoint character (not necessarily the main character) was a journalist and the show was framed as a documentary they were making about the Kamen Rider. Although it might be hard to explain how they got footage of the villains monologuing in a secret lair... Sorry, I'll stop before I get even more off topic.

"Now, don't quote me on this--" CUT TO VILLAIN SCENE

I really love this idea, by the way. A series where the hero is constantly addressing the camera, alternating between funny asides and diary-style melodrama, that sounds super fun. I think you could also have the same kind of fourth wall-breaking intros that Build had, and those were amazing.