"I was taking a walk."

No...

That's not it, Nagato.

You're tired.

You've been running around at the whim of Haruhi, protecting me, and probably doing other work without us knowing.

The weariness of it all must have built up...

"The error data accumulating in my memory database will cause a bug to trigger anomalous behavior. It is an unavoidable event. In three years, on December 18th, I will inevitably reconstruct the world. I have no countermeasure for it, because I do not know the cause of the error."

I do know.

What triggered the anomalous behavior that Nagato cannot understand?

What exactly was the error data that she's been accumulating?

It was the most basic of things.

Even for an AI that shouldn't stray from its program parameters, or for a robot, given enough time, it's natural for anomalies to develop.

You won't understand, but I do.

And Haruhi probably does too.

That, Nagato, is what we call emotions.

You were designed to be emotionless, so your reaction to it was that much stronger.

Every now and then, you must have wanted to cry or scream or yell "I don't care anymore!"

And even if you didn't think that way, maybe you should have.

We should have let you.

I'm also partially responsible.

I came to rely on her too much, just letting her deal with everything.

I figured that as long as she could handle everything, I could stop thinking.

I've been more of an idiot than Haruhi.

I don't have the right to point any fingers.

And as a result, Nagato was driven to the point where she wanted to change the world.

Bug? Error? Not a chance. That wasn't it.

This was exactly what she wanted.

She wished for a normal world like this.