It's not much later, in Isabella's room, that she asks:
"So... is Alex really a dom?"
"I mean, when you're setting the movie up, or between bites like we're doing right now, or before you go to bed, or after you wake up."
"Well, couldn't you? Next time you're having a not-sex time together, you could ask him not to use the whatever-it-was."
"'The thing you used last time' should be enough, unless he used lots of things, in which case you can try to describe it, or point at it when he tries to use it?"
Which isn't that different than the entire rest of this conversation. "Well?"
"Okay, but, like, you have to have a reason to think you wouldn't be able to do a thing. And, it's a relationship, so, by default you're assumed to be able to choose what things happen?"
"Um. No. No it's not. As far as I'm aware, and as far as all those sex ed pamphlets and classes say, the sub can also choose what goes on in a relationship, because relationships are supposed to be mutually satisfying," he explains carefully. "That is also the reasoning behind safewords and aftercare."
"Before we started going out, Isabella asked me to write a list of my interests and limits and stuff. I think the fact that it was a written list was more an Isabella thing than a common thing, but typically the dom is supposed to care what the sub wants, and typically the sub is supposed to be able to say it, especially if it's something they don't want. Again, safeword. Usually 'safeword' is the default safeword itself. But yeah, bringing it up by saying, 'by the way, next time could you not use that toy? I don't like it much' should cover you."