This one was good. Set in the "old world", during the series, it centers on the representatives of the three Japanese states and who they are and what plans they are brewing. Their target? Kamen Rider Build!

I loved Sento in this movie, when everyone forgot about him, when everyone - literally! - tried to kill him, mind-controlled by the aliens, and he had to find a way out of this mess completely alone because even Banjo and Misora were against him. And on top of that, he had to listen to Takumi's constant needling about how it was impossible to "fix" Banjo etc. and so on.

Speaking of Takumi, I love the "mind palace" where Sento keeps meeting his other self, all the doors, mirrors and stairs and whatnot. The CGI is perfect and visually, the "room" is stunning!

Also, AFAIR, Sento never told anyone about this, did he? That his personality literally split into Takumi - the him from before - and Sento - the him now. That he has actual conversations with himself, that he can hear and see his other self.

Gosh, Sento... he keeps so many secrets from the others, always shouldering everything, blaming himself for everything. And yet, instead of being all doom and gloom about his guilt, he fights for "Love and Peace". What an amazing character!