The controlled dialogue was not held at the Land of Rain's central base.
Nagato opened only a single paper mirror.
Obito appeared through a spatial projection with no fixed endpoint.
On Konoha's side, Gen sat with the Land of Rivers' recorder in a neutral liaison room.
None of the three parties could see the other two's actual locations.
The paper mirror could transmit only sound, surface chakra, and authorized images of evidence.
If any party tried to use the connection to locate another, the entire paper mirror would immediately dissolve into rainwater.
The dialogue record was also divided into three copies.
Nagato kept the Land of Rain's original transcript.
The Land of Rivers' recorder kept only each party's exact words and the evidence reference numbers, without recording the layout of the Akatsuki's base.
Obito's spatial projection left an independent echo that could not alter the contents recorded by Konoha or the Land of Rain.
The three records could later be cross-checked to establish who had said what, but none would let any party obtain the other two's secrets.
Nagato's agreement to speak did not mean he had agreed to an interrogation.
Gen could answer for Konoha's actions, but he could not demand that Nagato disclose all of the Akatsuki's members and capabilities.
Nagato dispensed with pleasantries.
"What gives Konoha the right to demand that the Akatsuki stop its Tailed Beast plan?"
Gen did not answer that it was because Black Zetsu had tampered with it.
That could only establish a problem with the origins of the Moon's Eye Plan. It did not automatically give Konoha the authority to decide the Land of Rain's path.
"Konoha has no such right."
Nagato looked at him through the paper mirror with his Rinnegan.
"Then why are you sitting here?"
"Because a Takigakure transport