So, she was right about that at the very least. It's possible for criminals to time traveler too. Unlike her, those people won't follow guardians' orders, right? They would either, one lash out, and two observe the situation. Observe, pretend to play along, and then take advantage of it. Either option will be horrible. Now that she has confirmed this, Setsura is worried. How many criminals from the future have come here? Not Meiji specifically, but other places in the past. How many rules did they break that ended up changing the future?
No, hold on. If they interfered with the past too much, then the future would not be like that. A future where even the simple negative thought is a bad thing. Where scanners monitor stress levels - where people go to therapy for mere outbursts.
"Setsura, the Guardians are.."