Set at the end of the Fullbring arc, right when Ichigo gets his powers back. I don't think we got any glimpses inside his head at this point but if there's anything that's like, super contradictory to canon please tell me!
"It's been a while, Ichigo."
His powers had been back for all of a minute. Couldn't his white double let him take care of Ginjo before pulling him into his sideways world?
"You're still here? I thought years away would have-" he was cut off by a swift punch.
"What the hell was that for?" It stung, but the hollow wasn't out to hurt him.
"A test. Had to see if you were real this time. Now that I have an answer-"
Ichigo flash stepped to another building, narrowly avoiding the follow up blow. What did the hollow mean by "this time"?
"You don't still think you're better than me, do you?" The hollow's voice came from behind. Before Ichigo could turn around, he found himself flat on his ass, his jaw throbbing.
"And years away would have done what? As long as your dumb ass is still alive I'm not going anywhere." He paused for a moment, glaring down at Ichigo.
"You left us here."
"I...yeah. I did."
"Up until a few minutes ago, this place was a crumbling, flooded mess."
The hollow smiled suddenly.
"I thought I was gonna have to kill you for that but it seems like you finally stopped lying to yourself."
Ichigo sighed and lay on his back. How did the hollow scan years worth of thoughts so quickly?
"What, are we having nap time?" The hollow stood over him, blocking his view.
"Shut up. I'm thinking."
"You've had years to think, Ichigo. Are you really that slow?"
"Probably."
The hollow laughed.
"You really have gotten more honest so I'll humor you. Let's see if you say something worth listening to."
"From the way everyone around me acted, it seemed like hollows were pure evil," Ichigo said finally.
The hollow scoffed. "And since when did you care what other people thought?"
"I know," Ichigo sighed again. "But that's why I tried to ignore you."
"You're back to lying already? I'm disappointed."
Ichigo lay still for a long time, trying to find the right words. His hollow was patient, not goading him into action or taunting him like usual. He wanted to hear this.
"If you helped me," Ichigo said finally, "I wasn't really winning. But you did try to help me."
"That's what you didn't get. I've been here since that day in Urahara's basement. Me and old man Zangetsu. Both of us. Both halves of you. I'd have helped you.
"So why didn't you let me, partner?"
A lump formed in Ichigo's throat at the note of sadness in his hollow's voice but he forced it down. He didn't get to be upset now, not after everything he'd put the hollow through.
"You called me partner the first time we met. Now I understand why."
"Oh? Do you?"
"Are you really gonna make me say it?" He stared up at his hollow, who for once wasn't mocking him.
"I am."
Ichigo closed his eyes. "You're me, just a part I tried to bury."
"Didn't work very well, did it?" his hollow asked softly.
Ichigo would have time to die and become a proper Soul Reaper before he finished listing everything that simply not ignoring his hollow would have prevented.
"No, it didn't. And I'm sorry, Zangetsu."
"Then prove it by not doing things that make you weaker."
His hollow looked like he had more to say but instead settled for, "You should talk to the old man too."
"Where is h-oh." Ichigo sat up and there he was, his coat somehow billowing in this windless place.
He went over and knelt before the old man, his eyes planted firmly on his lap. Guilt washed over him.
"I'm sorry. Just...I'm sorry. You deserved better than someone like me."
He had just been thrown into Soul Reaping. Save for the couple of months Rukia guided him, he had no formal training. If hollows died, he was doing his job right and that was enough. Except, it had never been enough.
Then came the execution and Aizen. He jumped into fight after fight, dragging the old man with him every time and Zangetsu wanted him to win. Helped him win. That was how he protected Ichigo. Then he'd gone and...he really was horrible to his zanpakuto, wasn't he?
"If you'll fight by my side again, I promise it will be different. I'm not like that anymore, and I would never ask you to-"
"Silence."
Ichigo bowed, his heart racing. He hadn't felt this nervous since the first time he was pulled in here and everything was collapsing.
"Sit up and hold out your hands," the old man commanded.
Ichigo did as he was told and soon felt the familiar weight of his sword. The shape wasn't quite the same but this...this was Zangetsu.
The old man said nothing else. He was trusting Ichigo, though he'd done nothing to deserve it. Hadn't had his powers back long enough to prove it. Tears welled up in his eyes but he fought them back.
"I swear I'll listen," he said, his voice wavering a bit. "To both of you."
"You better, Ichigo," his hollow said, holding his own white sword level with Ichigo's throat.
"'Cause if you ever make him cry again, I really will kill you."
The old man put a hand on the hollow's shoulder and he lowered the sword, clearly annoyed.
"Go," the old man said.
Ichigo found himself on his knees next to his body, Zangetsu on his back.
Years had gone by since he felt anyone's spirit energy. For a moment, it overwhelmed even him. He sorted through them one by one. Kenpachi, Renji, Rukia, Chad, Orihime.
Ichigo stood, one hand going up to Zangetsu's hilt. He held back a smirk at Ginjo's expression.
He'd win this.