Kashin Koji killed Ao in an instant without hesitation. But he didn’t kill any of the members of Team 7 even though Ao was his subordinate and Team 7 are nothing to him. Why save these Konohagakure shinobi? Also, in the last chapter, we saw that Delta wanted to kill the Konohagakure shinobi and retrieve Kawaki.
But Kashin Koji didn’t allow her to do so and persuaded her in his own way not to kill them and let them take Kawaki. This situation is a bit similar to Itachi Uchiha visit to Konohagakure as an Akatsuki member. Even Itachi could, he didn’t kill anyone. But at the same time, he did some damage to them in order to avoid suspicion. Let’s assume that he is from Konohagakure and the child of someone from this village. Let’s say Jiraiya is his father.