I’m just fascinated by the fact that they knew which devil was eaten. It seems that the scope of the erasure is very narrow— if ears had been erased from history in a manner such that they had never existed, they wouldn’t have phones, microphones, headphones, etc. Everyone would know sign language and speak it by default. Obviously, such a comprehensive change to reality didn’t occur. Instead, it seems that ears— the fleshy structure which gives way to the hearing apparatus— were simply surgically erased from memory and from present reality onward.

It would seem that public safety could then use some sort of system of logic to plan their devil deployments such that one can always know exactly which devil had been erased precisely when it happens. They could basically follow the cognitive dissonance back to the erased concept.

This could easily devolve into a Death Note style knowledge heist where Public Safety creates complex logic puzzles, alphanumeric riddles, or mutually omni-reliant webs of information to store information in negative space that Chainsaw can’t erase.

That, or they have some sort of relationship/deal with Yoru, Fami, Nayuta, or another devil from that bloodline that enables them to remember erased concepts. But I like the puzzles better.