Sasuke assumes the first comment is meant as a deflection, debating calling him out on it, but instead he decides to file it away for later. While he's hardly one for jokes he is one for avoiding his own personal topics when they're brought up against his will; this must be Sans's way of handling it.

"You changed to that topic quickly," he counters with little emotion, silent for a moment or two after. A less perceptive person might assume that he's irritated or that it's a sensitive topic, maybe, even with how calm he seems, but even beneath that neutral expression there's no real reaction. He's accustomed to talking about this.

"Does that mean that you haven't, if yours was so long ago?"