After all, Kabuto Yakushi was different from the Menma before him. His real body was right there. How could Naruto let him slip away over a few words?
Nominally, Naruto had come to investigate the disappearance of the Guardian Ninja at the Fire Temple, and that investigation was still ongoing.
A Konoha ninja had discovered a fugitive wanted by the village while out on a mission, so he was taking him back.
That was so damn reasonable it couldn't have been more reasonable.
Never mind a request from the leader of the Reshape Organization—even if a whole pack of Ōtsutsuki showed up now, Naruto had no reason to release him!
The only thing that surprised Naruto was that, when he reached the depths of the cave, he had clearly kept a constant lock on Kabuto's and Sora's chakra inside.
With the abilities of Six Paths Mode, he was absolutely certain no one had come into contact with them during that time.
Yet the leader of Reshape had detected the sealing jutsu marks Naruto had left on them from so far away?
Was it some special sensory ninjutsu?
"I was just fishing, but there really are marks... All right, then let Kabuto accompany Naruto-kun on his 'diplomatic visit' to Konoha as an envoy representing the Reshape Organization, as a show of our sincerity."
"...An envoy?"
"Yes. With an official designation, you can at least spare his life, right? I'll take that as your agreement." Menma smiled. "Well then, I'll be leaving."
Menma didn't press the matter any further, and his tone didn't sound as though he truly cared whether Kabuto stayed or left.
He even gave Naruto the impression that this mere verbal designation of "envoy" was enough for him to trust that Konoha wouldn't take any drastic measures against Kabuto.