Kanda's idea had worked. He had hoped using Ami as a target would have halted Chief's wrath. He wasn't sure how much time he had but he wasn't going to let them attack him, not until he said what he had to say.

"Look, hear me out." He started, bringing his sword to Ami's neck pressing it gently lest she move out of his grip and he lose his flesh shield. "You're right, I sold her out. Truth be told, I've sold you both out. That place you're looking for doesn't exist. This was all a plot to kill the priestess and believe me when I say I don't want that but Cortana had to be taken."

She had to be sacrificed, that was the plan. Had she not fallen then Metallia would have figured it out and they wouldn't be able to destroy her.