It would be too late.
They all took a part of him.
He could build wall after wall, defense after defense, and they would still find a way in. It annoyed him. It angered him. It made him try harder, just to keep them out, keep everyone out but it never seemed to work. Not really. They slithered through holes in the wall, surrounding him. Seeped in through the floor and wrapped around his ankle. Banged against the window, calling and scratching.
Leaving a mark.
That window, his weak spot, that one part of his soul he couldn't cover up and over. The weak spot he would never admit to having but needed all the same, because how else could he keep track of the world? Horrible, fucked up world that he needed to see to believe. Horrible fucked up world with horrible fucked up people that used and abused and killed. All of them scrabbling for something to hold on to.
So they peered in, fogged up glass and wrote secret messages when his back was turned and he couldn't defend himself. Left claw marks etched in- demons, humans, all of them scrabbling.
See, want, take. That's what demons did.
Only they couldn't yet, not quite. They could only chip at his surface. Piece. By piece.
And that's why he can never leave them. Not yet. He can't let them keep something of his no matter how small it may be. So he let's them have their little victories.
It's why he let's Hakkai give him gentle steel orders sometimes, with fake smiles and faker care.
Why he let's Goku tug on his robe and stare at him with hopeful gold eyes. Soft, strong, asking, shining like the coronet leash he wore.
Why he let Gojyo lean on him from time to time and steal a light, smelling like the wrong cigarettes and the wrong beer and the wrong /everything/.
Why he was so much more patient than he would be normally if forced to be with such people, biding time, keeping watch. They were too busy taking pieces of him to realize he had them all already. Too busy to look, really look and not just see, at what was staring back out at them.
But they'd see some day, when glass broke and walls crumbled and an empire of violet gold fell to dust and ashes.
See, want, take
They'd see what a real demon was.
And it will be too late.