He knew something about Marluxia at the least. Perhaps not what Larxene was concerned about him knowing (or perhaps it was?) but he knew something. Something interesting enough to bring him searching her out, instead of sitting like a spider in his web and pulling her closer bit by bit.

"Tell me," he answered, "have you ever considered what may come of us in the future?"

It might seem like a sudden change of topic, but it could also be taken to imply that her second answer had been correct and he simply hadn't bothered with the intermediate step of answering in the affirmative.