Of course Kakashi knew that they expected him to say something, to be – what? Shocked? Relieved? He wasn't too sure. Disturbed maybe. Yes, they probably expected the revelation of her identity to disturb him in some way. But even if he had known what his thoughts were as he was presented with proof for what he had not dared to believe, even if his meddled up emotions had not turned into stoic numbness before they even had a chance to show, he simply did not want to give them the pleasure. He complimented Sakura briefly on her find, but pointed out that her theory did not at all account for the means by which Madara took possession of his body, or connected to this world in the first place.
"I can't say anything for certain", Neji took his cue there "The first time he possessed you I did not know what I was looking at – my eyes may see a lot, but they aren't that quick in processing the information – and the second time, when Naruto possessed you that is, I did not see what happened at all, as you were inside here", he gestured at the building surrounding them. For obvious reasons the Hokage's Residence was constructed in a way that did not allow even the most skilled byakugan-user to see through it's walls.
"I also haven't seen you use Kamui often enough to be sure – but when he took possession at the cave, I initally thought you were using it there, judging by the chakraflow around your Sharingan. Though, of course it was covered at that time. Also", he paused for a second, seemingly searching for the right words to use „the Sharingan wasn't projecting anything, as it would if you opened an interdimensional hole somewhere, but rather opening itself..."
He waited for the others to take this information in, waited for questions to be asked, but they all just beckoned him to continue.
"As far as I can tell, I would say that during the second time, when it was Naruto, it was simply his conciousness passing over into your body. The first time however, when it was Madara himself, I'd say his spiritual energy was actually trying to assimilate your chakra."
"What?", Sakura blurted out.
"Chakra is-", Sai began to explain, but she cut him off.
"I know, I know.. Chakra is the resulting energy formed when the spiritual and physical energy react with each other", she quoted "but also acts as a transmitter between both forms of energy. The Yamanaka' mindcontrol, for example, works by suggesting the victims physical energy that the user's chakra is their own, thus controling the body, and genjutsu pretty much works the other way around; But why would he try to assimilate Kakashi-sensei's Chakra? How is this even possible?"
Her question was met with silence, which was eventually ended by Tenten.
"Anyway", she said, as she saw no use in pondering on something they, as it was, could not figure out yet "Why the headaches? Mindcontrol isn't supposed to hurt the victim physically, is it?"
"It could be, because the Sharingan is being controled remotely", Sai suggested.
"Also, if it actually opens itself, that's ought to hurt, right?"
"Could be", Kakashi mused, thought for a moment, then added: "Although it could also be, because I wasn't actually made to be used for this purpose."
"You mean", Sakura casually removed her foreheadprotector to allow her fingers to comb through her hair, as if in doing so she could make some air for her thoughts, "this – what ever technic Madara is using – actually would require a true Uchiha to be the reciever."
"So, on the occassions the headaches occured, but no possession followed", Tenten thought aloud "Madara was, like, only taking a peek on the other side."
They agreed, then were silent for some time. They all felt that, while they were getting a clearer view of what was going on, they still were no where nearer to actually understanding it.
"When did the headaches start anyway?", Sakura finally asked.
Kakashi shrugged. He couldn't really remember.
"After you left for Suna, I think", he said, after he had thought about it for a while.
"Didn't you check out Shikamaru's wall painting around that time?", Sai wondered.
Kakashi blinked, then admitted that he had no idea what Sai was talking about.
"Kurenai asked me to copy it. She said, you wanted to take a look at it, but apparently found nothing, as you never mentioned it thereafter."