At least there is a fantasy analogue Japan to be the origin of the Japanese stuff. Not like sometimes where it's "here's a country that is total European in look and design and setup except that everyone eats rice for breakfast."
Does anyone else find it a bit of a stretch that just now Mia is finally becoming aware of how badly her sister was treated? I'm not saying Mia is a bad actor, I think she genuinely cares for her sister(at the very least that's what the writing is suggesting), but it's just a lot to buy that she's only now becoming aware of it.
Regarding the first page based on context alone I assume fish eye is talking about dead fish eyes I.e. lifeless and without colour. As for corn on the foot I'm assuming that actually means Corn on the Cob.
"Corns" are slang for foot and hand calluses, at least in certain dialects. I'm guessing it stems from the size of the callus being roughly that of a corn kernel (much like the "corn" in corned beef refers to the size of the salt crystal used for brining) , but the use of the term dates at least as far back as Shakespeare.*
*sources: Boy Scouts handbook, The Three Stooges, and Wiktionary
I noticed the instructions didn't mention anything about leaving witnesses