The truth is what he doesn't want to accept, though there's no changing it. Shisui doesn't even know half of it, but it's just this gut feeling telling him that he'd failed. He'd failed Itachi.

Because...

"You shouldn't be here." Where is here, by the way? "I don't even know where here is, but if I'm here now, then you shouldn't be." He was dead, so why was Itachi here?

"I failed you, didn't I?" Because it wasn't Itachi he was rejecting, it was himself-- his incompetence to see that one thing through to the very end that could have saved them all. "I failed you." And his voice breaks again. Shisui swallows thickly, forcing that lump back down.

It's only fitting that he's on his knees before Itachi, because he ends up bowing his head to the sand, hands clawing in it while he struggled to get words out at all.

"I'm so... I'm so, so sorry. I'm so sorry... Itachi..."

And saying his name now, acknowledging Itachi-- it threatens to burst that dam inside. There's a hitch in his voice that hints at it.

"I'm sorry, Itachio...I'm sorry...I--!"

He cannot say it enough.