What Iris said look like it had shaken up Rel from his delusion of Na. He refused to believe Na was no longer in this world, that she had vanished and Rei's years, centuries of waiting was for nothing.
In the end, he couldn't even find her soul. Not a word, not a goodbye, not even an anger from her. Nothing. She had gone and it was Lu, who was with her, in her last moment before her soul was completely fussed with Iris. Just like how she wanted centuries ago, in her last breath.
Even in her last moment, Na only thought of Lu.
"She is not going anywhere. I am going to protect her." Rei gritted his teeth when he said that, as he moved closer to Iris.
"But, you are the person that she needed to be protected from," Iris replied. She moved back from him because she realized her predicament. With how strong Rei was, there was no way lis could fight him head on if she didn't think of a way to escape this situation.