Just like Sans is destined to know things he doesn't want to. Or at least that's how it would be if he believed in fate.

"i...can imagine."

He might not have been technically Asriel, but the flower still remained a real connection to Chara's past. Proof that they had once truly been human, had tried to do good--had once had hope.

Sans can hear the hesitation in Frisk's voice. Another thing they feel they need to be cautious talking about. It's understandable. Chara doesn't seem to like it much when people point out that there's humanity left in them.

yeah. makes sense."