Mary (sister from outside the domain) theory - Mary is SIS?
Again translation (of the most vital parts) of
http://conan-4869.net article. Very interesting!
In file 895 while talking with Yusaku/Subaru, Rei dropped a line ‘a scientist that invents gadgets that can put even MI6 to shame’. Wait a second, why MI6 suddenly? Knowing Gosho, it’s probably some kind of hint. Because… why, really? What’s the point of casually bringing MI6 into conversation?
Vermouth’s arc had FBI, Bourbon’s arc has Security Bureau in storytelling focus, maybe MI6 will belong to RUM’s arc? From this explanation, we can learn that MI6 is 'people who can create gadgets as complicated as professor’s’.
MI6 is called Secret Intelligence Service or SIS. We also had some theories that Sera lived in Britain instead of being American (Sera uses British English).
We also have a possibility (TN: strong possibility) that Elena (British) and Mary are sisters.
Vermouth - FBI, Kir = CIA, Bourbon = SB, so RUM could have ties to MI6.
IF we take [imouto]’s translation as [sister] and then make it SIS, and [ryouiki] as [area], [territory], then ryouikigai means [outside of the territory], probably SIS, that’s outside of Britain.
Or maybe another possible solution.
領域外の妹 = 妹 (sister), 領域(territory-TER), and if we take 外 as (out), then we can have something roughly sounding like
'Sister’ without 'ter’ part. Which is SIS.
