He wonders about that. At a time, his purpose seemed so clear. Now, he's not so sure. Nevertheless, 9S salutes, left hand over where his heart would be, if he had one.

"My role is to assist in the war against the machine lifeforms. Ever since the machines took over Earth, the humans who survived have been in hiding on the moon. So us androids fight in place of humans. I'm a Scanner, so I scout enemy lines and gather information, that sort of thing."

He's technically not supposed to be able to fight, but he can. Not as well as a combat unit, though.

"Once we eradicate the machines, the humans on the moon will be able to return to their home on Earth."

But he's considering turning away from that purpose. If only there was a way he could fulfill it without being YoRHa.