I believe they were referencing Bakura for your Jekyll/Hyde reference.

Okay, but I was asking about evidence from Kamen Rider Revice

I should've been clearer before.

Closest thing are the Imagins from Den-O replacing their host's personality with their own.

Today I learned that Vice might be based on Riderman

https://streamable.com/shvwdf
Swordriver has sounds for a kyoryu combo. Revice books?

Iiiiii~nteresting...

Also, frankly insulted that the video doesn't show what happens when you insert two 'books' instead; it's just one and three books. Also, what are those things? Magnets?

Is it possible to just take out the chip or whatever out of these toys and upload their contents onto a computer to see everything that's in them?

Probably not. If it were that easy, I would have grabbed the voice lines they provided for the P-Bandai Rekka on the website and then played around with it. When I downloaded it, it wasn't a simple .mp3 or .ogg

So you tried? Out of curiosity, what kind of file was it?

It's a r.20 file, idk what's it about.

Maybe try looking for programs that can open r.20 files. I don't know what it's about but a quick search shows me that there's a lot of programs that can open those things, most of them Windows only.

Is this file taken from the Swordriver?

It's the one I took from the website. Assuming I read correctly, you're supposed to just put this in the Rekka SD Card.