I've been rereading Bleach and this just kinda jumped out at me. I mean, I know that Tsukishima aimed to replace Ichigo in the minds of both Inoue and Sado, but didn't take that exact approach against Byakuya. Still though... his best friends had no faith in Ichigo, and I have a problem with that.
"I cannot begin to repay the debts I owe you. Such is my gratitude. However, you are an enemy of Kurosaki Ichigo. Debt or not, I feel no remorse cutting you down."
Memories of all the times his opponent helped and guided him surged through Byakuya's mind, but it couldn't be helped. He could simply not erase the look on Kurosaki's face from his sight; lonely, hurting, and so, so, betrayed.
This child that had shed so much blood for the Soul Society, given up so much, and in return they leave him at the mercy of a madman like Ginjou. Byakuya felt physically sick.
But no more of that now. Rukia had successfully cut the boy with reiatsu blade, restoring Kuroskai's powers, so that he was no longer defenceless or dependent. The arena dissolved and Byakuya started moving toward the remnants of his sister's reiatsu.
As he left, he failed to notice a certain shopkeeper smiling at him from behind the trees.
Urahara had been caught in the arena with Byakuya and Tsukishima and so watched the fight, wanting to know the details of Tsukushima's peculiar gift. He had heard that the effects would be dispelled with the man's death, but he didn't want to take the chance that such a tactic failed.
He also knew that, had Kurosaki killed him (and he would) and the effects were dispelled, it would still haunt the boy forever.
But what the shopkeeper had learned here was sufficient enough to deprogram both Sado and Inoue in the event that there was no way to reverse the effects. Which was especially good given that the pair in question was coming around. Inoue spotted him first and confirmed Urahara's fears:
"Urahara-san! Is Tsukishima-san ok? Is the fighting over? Do you know why Kurosaki-kun was attacking him?" The look Sado was giving him mirrored all of Inoue's questions and confusion. The shopkeeper sighed and sat down.
"The fighting is over for the most part, but there is still one battle going on. Kurosaki and Ishida would be dueling with Ginjou Kuugo now. The boy, Yukio, has them locked in a separate arena where we can't interfere. Now, I must ask you something very important," Urahara stared them both dead in the eye.
"For as long as you've known him, when has Kurosaki ever attacked a friend for no reason?"
"Never! Kurosaki-kun wouldn't attack anybody without reason!" Inoue was emphatic in her defense of Ichigo, even as she crucified him. "Something must be wrong with him, for him to be trying to hurt-"
"Or maybe something's wrong with you two? Something's happened to you, something you don't remember? After all, we all know how Kurosaki gets when the people he loves get hurt." Sado nodded, conceding that Ichigo would most definitely lose his temper over something like that.
"But even if it were true, why would Ichigo think Tsukishima-san was the cause? I mean after everything Tsukishima-san's done for us…"
Urahara sighed. "Maybe we should compare notes: you both have memories of Tsukishima-san, correct? Memories that go all the way back to your childhood?" The teens both nodded. "Now how can that be, when Sado lived in Mexico for most of his life while Inoue has always lived in Karakura Town?"
Confusion painted both their features. Urahara continued.
"Now, we all know that Tsukishima has a Fullbring called Book Of The End, in which his bookmark becomes a sword, yes? Good. What I've come to realize from the battles just now, is that the sword is not for cutting exactly. In fact, the nature of Tsukishima's Fullbring allows him to avoid confrontation in general." The shopkeeper paused to make sure the pair was still following the conversation. "The Book Of The End can insert Tsukishima into the past of whatever he cuts, in whatever way he pleases."
A kind of horror had settled into Sado and Inoue's eyes. Quietly, Inoue asked how Urahara had come to that conclusion.
"I watched the battle between Tsukishima and Captain Kuchiki Byakuya; apparently, Tsukishima really likes to talk and he himself explained his power. Captain Kuchiki himself got caught pretty significantly. Not that it ended up mattering."
Sado looked up. "What do you mean it didn't matter that Kuchiki got cut? Did Tsukishima-san's power not work on him?"
"No, no, it worked fine. Captain Kuchiki simply didn't care that he was cutting down his… tutor, I think? Maybe oldest friend, I'm not sure. Either way, the fact that Tsukishima was Kurosaki's enemy made him Captain Kuchiki's enemy too. To be honest, it was the kind of behaviour that I had expected from you two."
With that, Urahara stood to leave. When Inoue asked where he was going, he explained that there were others he needed to deprogram. "Tsukishima hit every friend Kurosaki ever had, and both his sisters. If I think about it, he got a lot closer to hitting Kurosaki where it hurts than any other enemy Kurosaki's ever faced." It was that thought that Urahara left them with.
Later that night, Tsukishima succumbed to the wounds Byakuya dealt him and then neither Sado nor Inoue remembered anything to do with him.