This story takes place after episode 219, so ignore anything that happened in the anime or manga after that point.
...
The battle with Aizen was over, and soul society had won the war. All but Yumichika, who had lost everything. For he had lost Ikkaku, not his life, but his trust and his love.
Yumi had always firmly believed that he would rather die than let Ikkaku see his zanpakuto's true form, but he'd never thought about what he would do if it was Ikkaku who could die. He'd never really considered what lengths he would go to if Ikkaku were in danger of dying, if the one he loved, if Ikkaku would die. The idea always seemed preposterous, Ikkaku was too strong. The only ones stronger were captain Zaraki and Ichigo, and Ikkaku wouldn't be in danger from them. As such it had never crossed his mind that Ikkaku could lose a fight, it would be like him loosing a beauty contest, totally impossible.
And yet the impossible happened. Ikkaku lost. Yumi still couldn't say for sure what had happened, since he had been fighting an arrancar of his own. He had only realized what was going on after Ikkaku had fallen; when he saw his bloody body fall to the ground and not get up again. Everything just went dark before Yumi's eyes, he couldn't see anything but Ikkaku laying there, he didn't even remember how he got over to him, later others told him that he'd fought off Kira and wounded him when he tried to stop him. But all he could remember was dying to get to Ikkaku to see if he was alive, and then suddenly he was there, cradling Ikkaku's bleeding body in his arms. He almost started sobbing when he realized that he had a heartbeat, although a faint one. But crying hysterically is just so unbeautiful, so he couldn't do that. But seeing him there, something inside Yumi just broke, his control, restrain, everything was gone. Before he'd even had time to think, his zanpakuto was out and he was calling its true name, and he had drained the arrancar that had hurt Ikkaku of all his reiatsu.
The consequences of this never even crossed his mind. But as the arrancar disappeared in front of his eyes, he froze, realizing what he had just done. He felt afraid to turn around, but Yumi reassured himself that Ikkaku was unconscious, so he could come up with a plausible story to tell him later. In true Yumi fashion, only the opinion and existence of Ikkaku mattered, he didn't think about what he would have to tell all the captions who also had been watching this scene. Yumi turned around, realizing he needed to get Ikkaku medical attention immediately. And upon turning his eyes instantly met Ikkaku's, and he felt as if the ground had dropped out from under him. The look of shock, horror and betrayal in Ikkaku's eyes, eyes which were rapidly showing disgust and rage, literally left him speechless. Yumi opened his mouth, and then closed it, several times. Searching for the words, but finding none. The silence grew as Ikkaku slowly lifted himself off the ground, blood from his wound dripping down his body. Yumi made a move as though to help him, but was immediately stopped by Ikkaku's cold glare and even colder words.
"Don't! Don't even come near me, I can't even look at you!" He snarled before turning and slowly limping off.
For a long time Yumi stood there, his only movement the slight shaking of his shoulders and the tears running slowly down his cheeks.