Well at first the anger is expected. He even smirks- after all the hell this guy (admittedly unknowingly) caused him, he deserves it! Asshole.

But then....then it gets weird.

"O...oii..." Really weird. Like possession, he wants to say, or... "...Oi, th' hell's goin on w' you..?" he starts, narrowing his eyes. He's about to act more seriously on the question- maybe grab for the other, try to sort it out. Except then-

They ARE the Items-

Katsuya drops the stick.

Takes a step back, once again.

"Th' hell do you mean, 'are'?" he manages to croak out, eyes wide with growing horror. This time it's not a flashback he's having. It's a proper memory. A real one, from the computerized world, with the chamber of unknown, unspeakable horrors-

'What happened here?' he asked, unable to see what sat in the great stone.

'Tragedy, Merea,' spoke the white spirit.

"Th...There's only seven righ'?" he weakly protests, even forcing a 'smile' to his face as if it could convince himself that it's some cruel joke he's being told. "There were seven, y' can' put... ninety...n..."

He shakes. He keeps shaking, but this time instead of a memory it's just from horror.

"That's why..?"