User blog comment:KasuraS/Aldebaran and Ram/Rem's Past Theory/@comment-30035163-20170812021849

With everything together, I agree with you that Al's focus was on Rem and not Ram. He's too friendly towards Ram in the sidestories, and he's perfectly chill when he believes Rem is Ram. Though the WN notes he was staring at her for a suspicious amount of time, which he played off with a joke about needing to fill up on Maid ingredient.

It's hard to tell if Al was at the village himself, but I doubt it. The Witch Cultists who survived the incident weren't really surprised by both Rem and Ram being alive. Or more exactly, they outright knew both sisters survived.

Which might indicate that there was a later incident that Al would have thought one of them, probably Rem, died during. It's important to take know that Rem's ability to smell miasma isn't a universal Oni trait, and actually seems to be a sign of something Witch Cultists poured into the ears of some Oni as it's shown in the Re:IF story.

I think Al knows something about Rem, or what was done to her, and whatever that was is enough to make him uncomfortable with the fact she's still alive. And he can't even deny it by pretending he misremembered her name or how she looked.