Shiro's eyes narrow, and his voice is harsh, as he replies,

"Do you always enjoy it when a broken soldier can doubt own sanity? I know what my problem is... probably. It's trauma. Same as after first escape."

But after first escape, Shiro was only hearing own voices and own memories, in nightmares. Not another very particular voice when wide awake.

He knows that, he knows that, and yet- this is all - this all not right. And maybe this conversation isn't right. Yes, that's it! This is a mistake.

Pain. In his head. His own. And anger. His own. So what would any other voice have to do with that? How can he converse nicely when it's hellish pain somewhere deep inside? And besides. Maybe there's no voice. Just like his memories are his own.

Something's wrong. Something's wrong.

Maybe this whole talking with a strange detective is what's wrong. That'd make sense, wouldn't it? And that's the young man's own thoughts. Because of the pain.
Something... something was wrong before the conversation, too, and he knows it. Waking up slightly wrong. Every day.

But it's fine, as long as everyone else is fine.

Yes,

Just let it be.

What could be done, anyway?

Wrong. Something is wrong.

"Now shut up, Holmes, you quack detective, and lay off, I'm not your study subject!!"