[It feels like he is listening, but she's so caught up in her fear that she isn't able to process what he has to say. So, she had a vision. So, she knows what she could become. None of that holds here. Rey says that if she goes back to New Amsterdam, she'll see herself go dark. But he knows that isn't possible, not while she's torn away from her powers.

But that's logic. When the Dark is infecting the mind, there is no logic.]

You've already given in, [he says, knowing that it won't be easy to hear. It wasn't how bluntly he wanted to say it before.] Hiding here. Being afraid. Telling yourself that that you have to stay here until you know you won't. Isn't that just the Darkness speaking right now? Isn't it already controlling everything you do? You're letting it infect your mind. You think you know what you're doing, but you don't. Not when it's like this.

[Riku knows that he's lucky. His mastery of the Darkness led to him being able to become immune to the most sour of its effects. It's a part of him, and he knows it could prey upon his mind if he let it—but that's just how he thinks. How he feels and handles things. How he assesses what's right in front of him. It's his own thought processes that made him susceptible to the Darkness.

Just like Rey's thought processes are doing the same to her.]

You aren't mastering it. You're letting it win. But if there's more Dark than Light in you—then you need to face it head on.

[He's already said, "You failed," essentially. He won't say it in other words yet again. The meaning is clear.]