[The question is not what he was expecting Cy to say next. His own expression creases with — surprise, before it softens, hesitation hanging like a hook on his immediate instinct. It has nothing to do with the request Cy has made of him. He would agree to that, and far more, without second thought.]

Do you remember when we first began discussing pain play? I mentioned that I've had difficult experiences. But more than that — I'm not sure what my reaction will be when triggered by those memories. That's probably why you're asking to try it during genjutsu. Isn't it?

[Cy knows him well, and even without specifics, he's told the man enough information about his eyes that things can be extrapolated.]

I'll have more control there. If you're all right with the potential for the scene to... stop, or end abruptly, then I'm willing. I won't lash out at you in the illusion even if I respond negatively.

[Perhaps Cy doesn't need to be told this — but given the knowledge that Cy's mind is not just his own, it's worth the clarification to Sasuke.]