Naofumi has a history of sleep paralysis... he even had it the night of his summoning, completely aware of what's going on. He talked about it with the other heroes. The next night, he experienced it again, this time aware of someone stealing his stuff.
At the trial, he explains himself, "I have sleep paralysis. I couldn't move but was aware of everything that was happening... including someone stealing my stuff."
The other heroes all agree that he didn't do it as sleep paralysis is a thing in their worlds as well
The charges are dropped, and Naofumi goes free but still has trust issues.
Later, when rooming with L'Arc, he experienced sleep paralysis again...
L'Arc talked about killing the Cardinal Heroes in order to save their world, unaware that Naofumi is awake and hearing everything he's saying.
After L'Arc leaves the room, Naofumi clenches his chest, resolution in his eyes but with his heart aching.
He makes preparations for his fight to the death with L'Arc while still hoping that they can resolve this without killing each other.
