I'd always assumed what you had about the main house, especially that Kyo lived "inside" as a child. (It would explain how Kagura so easily stumbled upon Kyo, why Kyo's childhood home looked so gated and was landscaped so similarly to vol 2's inside, and Kagura's comment that they would "sneak out of the house" to be play in the field near the main house. Also Kagura's comments that Kyo might be upset that the "Sohma main house is right over there.")
Now that I look at volume two, in the little map of the estate it says this: Main house (inside) when referring to everything inside the gate.
I like your explanation. The whole thing has ALWAYS confused me. A while back I wondered the same thing about Kyo going to the estate during New Years. I think I wondered if he was planning on sitting around Shishou's house by himself for three days, but it being Kyo, I'm sure he A) didn't think that far ahead and just caved to Tohru or B) really was planning on doing that.
And when Kyo says it was only the second time he'd been inside the main house, maybe KYO meant the building itself. If Kyo did live inside the gates as a child, I doubt his parents let him leave the yard, which was gated. He and Kagura snuck straight out, so Kyo really would be lost on the inside. Plus Kyo has this general denial of that period of his life, and I'm really not sure he would count it since he was so young. Of course I'm super tired and I have a killer migraine, so I'm pretty sure I'm not making sense.
But I like your theory!
