A/N: This is written under the assumption that Aizen was never captured after the Winter War, and went back to live in Hueco Mundo. There's also the assumption that at least some of the arrancar are still alive.
Sousuke opened his eyes, and the sadness overtook him immediately. He found himself clutching his pillow tightly to his chest, so desperate for it to be the warmth of his absent lover that he could almost smell him. With each flutter of his eyelids he entered farther into wakefulness, and the pain went deeper, stabbing at his chest until he was fully aware. He would never admit to anyone else that he still missed his fox this deeply, but he did. He sat up on the edge of the bed, tossing his legs over the side and staring blindly at the pure white of the wall ahead. The worst thing about heartbreak, he thought, is that every individual's pain hurts worse than anyone else's. He sat there hoping that the room would move, change, do something to give him comfort, or relief, or answers. But no matter how much he wished otherwise, the room was just a room, and he had no choice but to get up and carry on with a mockery of the life he remembered living.
Sousuke walked out on his balcony and looked up at the moon that rose permanently over Hueco Mundo. He could remember so many nights when he and Gin had sat on this same balcony overlooking the sand, having their evening tea. Those were some of Sousuke's favorite memories. Often after the tea was done Gin would cuddle up against his side, and they would enjoy the night air together. Now remembering these things only brought him pain. He had truly loved the boy, more than he had ever meant to, and now he was paying the price. This was what indulging in human emotions did for you. Sousuke closed his eyes tiredly. It was only morning, but he was always tired, now. Every moment felt like a constant struggle, as though he now carried the weight of the world he once meant to rule. Now there was only emptiness.
Despite the pain, he still had a kingdom to rule, if you could call it that anymore. While he still formally ruled over the Espada, there was no desire for war now (because why would he want to rule anything without Gin at his side?), and he mostly left all the arrancar to their own devices. He had no need for them anymore, and he kept them around only for servants. In the beginning, right after the war ended, some of the less intelligent ones tried to approach him, to speak to him, but by now they had all learned it was best to leave him alone. Even now, a year after Gin's betrayal, Sousuke was still mourning him as strongly as he did that first day, and none of Las Noches' other inhabitants wanted to be caught up in his well of sorrow.
It wasn't that Sousuke was angry. Not anymore. He still had his fits of bitterness, of course, and on occasion one of the more observant Espada would catch a flash of pain in his eyes, but for the most part, he was as calm as he had ever been. The difference was that the confidence was gone, along with his expression of shrewd calculation. What was left now was only a shell, a hollow casing of the man that once thought he wanted to be God. He had discovered, though, that he didn't want to be anything without Gin in his arms. He would have given the boy everything, and yet he managed to take the one thing Sousuke never expected. Sousuke had never doubted his loyalty, never thought to. Humans had a fondness for saying that "love is blind", and he finally understood that now. If he hadn't loved Gin so deeply, he may have been aware as to what was coming, and not be feeling this emptiness now.
But thinking about what could have been didn't change the present, and as Sousuke looked at himself in the the mirror, he couldn't help but notice how much he had changed. His shoulders were hunched, and all the color was gone from his skin. His hair was grown halfway down his back, not because he liked the way it looked, but because he couldn't find the motivation to have someone cut it. Nothing held appeal for him anymore, not without his fox. He just couldn't bring himself to care.
And, not for the first time, Sousuke sadly realized that he didn't want to be alive. He really didn't. He didn't believe in suicide, though, at least not for himself. Even this broken, he still held the vestiges of the belief that he was a God, and he couldn't bring himself to destroy something like that. And, even if he could, the real reason for not allowing himself death (though he would never admit this, even to himself), was that he couldn't bring himself to desecrate Gin's memory in that way. He still held on to the belief that Gin had loved him, despite his betrayal, and Sousuke couldn't do that to him. He couldn't hurt him in that way. Instead, he stood up straight, steadied his gaze, and began to prepare for the day.