Fugaku had been drinking tea on the porch and reading a progress report on the party preparations that the clan had been roped into in order to keep an S-Class shinobi from indiscriminately killing members of the clan at a time when everyone was needed while Sasuke trained. He had been reviewing the figures for the proposed refreshments budget when he had heard a startled yelp. Looking up, he found That Man holding his son who was futilely trying to attack him in order to free himself. As he rose, preparing to do battle to possibly futilely protect his child who'd probably die before he reached them, his eyes shifting from their three-tomoe Sharingan to something he'd been hiding for a while now which had been held in reserve for the final stage of the Coup, That Man smirked and made a handsign that indicated he wasn't there to fight.
"Don't worry Fugaku-dono. I'm just taking Sasuke for a playdate. He'll be back in time for dinner." That Man said as he shifted Sasuke into a position that was meant for easier carrying.
That Man whom Fugaku hadn't fought the night before because he'd been caught by surprise, had no idea of the man's true capabilities, and the gods only knew how many of his clan would've been killed during the struggle if he had. That Man whom Fugaku was humoring because his abilities and capabilities were as yet unknown due to the fact that the Mangekyo tended to be a bit of a random S-Class grab-bag, and the entire clan was the hostage in this case. The second That Man finally slipped up however...
"And, who or what is this 'Playdate' with?" Fugaku asked, having mentally noted that the man had not stated that his second son would be safe during said playdate or that the boy would be alive and unharmed when he was returned "in time for dinner".
"Why, Sasuke's bestest friend in the whole wide world for going on two lifetimes now." That Man replied.
"And, who is this person who's supposedly 'Sasuke's best friend'?" Fugaku asked, knowing that the closest thing his son had to a "Best friend" was his older brother. While the boy did interact with other children, none of them had ever stood out enough to be considered for that title.
"Well, if the Sage of the Six Paths is to be believed..." That man said as he pointed at the Shodai's face on the Hokage monument. "He goes by Naruto now though."
Fugaku felt like burying his head in his hands and groaning, which would be an utterly stupid move considering the fact that there was a dangerously insane indivdual on his property holding his son who he was apparently taking to go play with the Kyuubi Jinchuriki with whom he was strangely obsessed for some reason. Considering the brand of crazy That Man was, he should never have expected anything resembling a sane answer from him.
"Now, I'll just be taking little Madara here..." That Man said as he turned to leave for parts unknown with his child who was apparently being taken to play with the Uzumaki whether he wanted to or not.
"His name is Sasuke." Fugaku found himself pointing out.
"Sasuke, Madara, same thing, they're both Transmigrants of the Sage's elder son." That Man said dismissively. "Never did get that whole thing to tell you the truth. Just remember Naruto and the other one waking up from the dead with new tattoos and a major power boost and saying something about how they'd been the Sage's kids in a previous lifetime and how Hashirama and Madara used to be too before they died."
"You're claiming that..." Fugaku started. He didn't get a chance to finish, because That Man continued talking.
"Which of course begs the question of exactly how both Hashirama and Madara could be summoned with the Edo-Tensei while Sasuke and Naruto-kun were still alive. Unless, the Edo Tensei had siphoned off some of their Chakra and all of their previous life's memories and...But, then Madara came to life..." That Man said, apparently lost in his own world, not even noticing Sasuke squirming and kicking in his attempts to be free.
"Oh well, whatever." That Man said, dismissing whatever deep metaphysical subjects he was pondering. "Have to get Sasuke to Naruto. They're best friends you know. Of course, if I'd had a best friend like Sasuke, I would've killed him ages ago, before he got a chance to punch a hole in my chest."
"But, then again, what am I saying?" That Man said. "I pushed a complete asshole out of the way of a boulder at what I was sure was the cost of my own life, gave him one of my eyes too, and he goes and repays me by murdering our other teammate."
"Why," Fugaku started, not even believing he was about to suggest this given the potential fallout, but considering that That Man was edging into dangerous territory and looking like he might change his mind about keeping Sasuke alive to play with the Jinchuriki... "Why don't you bring Naruto here instead? Mikoto would be happy to have him over for dinner."
That Man turned and gave him a sharp look, his Mangekyo focused on him. In each eye, a different pattern. One of them matching the description of Uchiha Madara's "Eternal Mangekyo".
"Itachi told me about how you were going to be the one to rip the Kyuubi out of Naruto in order to control it during the Coup." That Man fairly growled. "Only way I'd ever bring Naruto here would be over your dead body. And, possibly your wife's."
Fugaku's moment of shock over That Man's knowledge of that part of the plan apparently gave all the opening That Man needed, because That Man turned and Shunshined away with Sasuke. When Fugaku went after That Man an instant later, it was to find that That Man was nowhere to be found at what should've been the Shunshin's endpoint considering That Man's trajectory.
Sasuke was gone, and Fugaku's only hope of seeing his son alive again was that Sasuke would keep the Jinchuriki entertained enough that That Man would allow him to live long enough for a second playdate.