Whoa, now that would be a great twist
I think Tanaka has something else to lose. I respect his loyalty to the Phantomhives, but I think he's got something darker to protect. A person, a secret, or both.
My guess is that it has to do with Claudia, or (and I can back this up) Frances Midford, the Phantomhive daughter.
true I mean we still dont know who killed the parents. and we dont know why undertaker was friends with the phantomhives. so many mysteries
If Undertaker was "friends" with anyone, it would have been friends with benefits ;]
(I mean, have you seen how similar he looks to Vincent and Frances?)
I think tanaka knew their plan and is on fake ciels side. and you know someone has to stay behind and find the reasons. I mean he's smart he can't just be compliant all of the sudden he has to have a plan himself too