[If Mikasa was older than average in her world... it gets her another look, as though he needed to remind himself of her apparent age. From a world either on the brink of ruin, or well past it, for something like that to be the case. A similar thing had happened to the mortal populations on his world, immediately after each Calamity.

But they always hung on, as vermin were wont to.]

I wonder... I admit I haven't paid particular attention to the Bonding habits of the locals. Perhaps a businesslike tying of the souls is unusual to them, and they assume all who pass before them are already emotionally bound together- either by romance or friendship.

[But he didn't think they would make the same mistake with them.]

Or, I can well imagine your other Bonded's... personality leading to something of the wrong impression.