^Well it is indeed strongly implied that the Takara's has Tsukumo - plus she has to trust them to be able to let them borrow/take her mascot. If the mascot was only thing that reminded of her sister, I would as her not let anyone take it on light reasons.
But I bet that Illuminati (more likely Gedouin) wouldn't keep the promise not to find Tsukumo - if the bloodline and research was important, like we know now, they wouldn't risk it. What I an after, Takara's are powerful and protecting Tsukumo (and Mephisto is propably in allegiance with them, he has his fingers on every plan). Thus I doubt after adoption Tsukumo's legal care is 100% with her new parents' hands, not in Tamamo's. Or at least adoption I know goes like that. And the child which isn't given up to adoption, Izumo, is still under care of her mother - so that is how Illuminati can forcefully put Izumo to school's and use her mother's name to do things legally.
(Though Tamamo give personally the right to adopt Tsukumo, it isn't legal but I doubt it isn't important, but I usually think detailed...)
Hope we find out of Takaras soon!
But Archer: the puppet INDEED looks like something of Mephisto's creation: the umbrella for example look very similar. And it is pink and it summons things out of nowhere in A puff - time and space demon to me!!
Now I can't get past the fact, I want to know the truth!!