Even if it's not as common as today it was used in large quantities as a preservative. So the smaller quantities used for this wouldn't be too far off once in a while.
@KediKopek I think you misunderstood him. The argument was that she can spend that time even on the most trivial magic. Getting a far deeper understanding of how it works than anyone else.
@spiderbait you are making two assumptions:
1 - Demons have a similar enough mindset to be able to understand humans
2 - That these demons can survive without human meat. (e.g. they need a nutrient that only humans produce naturally.)
The first assumption is somewhat questionable in this manga...
@mase_aga @Iwizesol it's the compression that's corrupting it. If you select "original image" it's fine. This is also the second time that I've encountered this error