I must've missed the scan that Ryuki Arms was on, unless it just wasn't posted here. Or I didn't look hard enough at the scans I did find online.
Something came to mind regarding Mitchy's likelihood of sticking around (though I'm of the mind he'll become the final villain), it's one of those "probably a coincidence" theories but I thought I'd share out of interest.
Our first death of the series is Yuuya, who we don't know a lot about. All we know based on context is that he was offered power from Sid and he took it. He seemed to find it interesting, which to me says he liked that power. He of course died to a slightly unrelated cause, but then...
Hase ate Helheim fruit because he thought it would give him power, since the fruit is tied to Lockseeds and he was trying to find replacements before. Greed for power did him in.
Sid was next, who blindly tried to take the fruit of knowledge from Roshuo, not realizing he could die at that moment. As before, greed for power was his downfall.
With the latest episode, Mitchy has gone from "I'd rather be friends with a god who I can manipulate" to "I AM GOING TO BE GOD", so we know now that he's got a greed for power... if this is a theme with the deaths, how long do you think he'll last?
Once again I fully admit this is not the strongest theory, especially since Kaito is all about power (though you could argue that he's the exception because, y'know, secondary Rider writing shield). I fully expect Mitchy to die by the end of the show, but the fact he's gone through this recent change of character... it's definitely leading up to SOMETHING, sooner or later.