Water pumps are actually one of the easiest "modern" inventions to make. It's a piston. I'd expect anyone that has spent time studying cars and combustion engines, to be able to figure out how to make a water pump. Admittedly, I grew up in American suburbia, where people were pretty obsessed with cars. I have no idea how common that sort of knowledge is in Japan.
A water pump is a piston, two valves, and some pipe. That's it.
Right, their function is obvious enough, and ‘simple’, but many of the settings they land in only use metal for weapons/armor and cookware. Hell, the simplest part of that is the pipe, and unless their society already knows how to make pipes (and will be thus mostly unimpressed with your water pump): that’s an instant dead end for most people.
I’ve got welding stuff out here, and all kinds of modern equipment, but if you told me to make a pipe one day: I wouldn’t have the slightest idea where to begin. I’ve never made a pipe before, and even as obvious a thing as it is ‘cylindrical (doesn’t have to be cylindrical) shell of metal with only two openings: it would still take me days of iterating with each of the materials (do I hollow you out, do I melt you around an object and hope that when it cools it releases the ‘form’, what do I do with my waste-bits?)
Knowing how something as obvious as an *axe* works doesn’t mean a person also knows how to bind the head on (assuming they even could make the wedge in the first place) securely. If you find yourself in a random place, with no modern tools, and no ability to simply look up the things you’ve forgotten: very few people are going to be able to valve their pipes and secure a pistoling mechanism within them.
There are many simpler mechanisms that are also easier to make as well. If someone has already got a well: hooray, that was step one... but why not instead make them wooden wheel with some notches in the outside, a wooden pole to stick it on, a smaller wooden wheel, and attach a handle to the little one? It’s just as obvious a technique for the job, and it’s made of wood (far more plentiful and easily worked with than metals (which would be mad expensive in all likelihood)).
As we are tragically short of magical powers as a species, there are many reasons that human cities are usually founded on rivers. In ancient terms: don’t have to build even a well, which is great, because you don’t have shovels. In medieval terms ‘hey, this well only has to be a couple of lengths deep!’
If I isekaid near to a river where the first aqueduct is mine: I’d build a bathhouse. No piping necessary, and they wouldn’t have to step into a probably deep and fast flowing river just to have a rinse.
Next contribution: if they’re a transmigrated Japanese woman: they always know not only how to build soap/distill ‘essential oils’, but how to package it in roughly the necessary amounts. ‘How’d you get your hair so silky and shiny’
–Antisosial MC sudenly becomes a sosial god.
“Cold reading is a specialty of mine.”
Says the young Japanese gamer who last interacted with people in the real a decade ago.
In theory, theory and practice are the same. In practice, they are not.
If half or more of your classmates in highschool know how to play the guitar, with a handful being really good at it and also only a handful having no interest or knowhow whatsoever, then you'd think it's normal to know how to play guitars.
You can be the world’s greatest guitar player, and if you arrive in a world with no guitars: what’re you gonna do, make one?
Oh yeah, the scurvy thing is mindblowing! I can understand remembering the treatment because it is something that I learned in school, but... The symptoms? Absolutely not.
I know the bleeding gums, but if I was faced with a person from back then who had scurvy: I might well just think they had gingevitis (also very not good obviously, but I don’t think eating their veggies is gonna fix that one. Dental hygiene probably isn’t a common element in such a world... I much prefer my plastic monstrocities over any hair-bristle brush from an animal >__<)
On the same page as the slaves, the transmigrated protagonist almost always finds themselves in the upscale part of the city, and if the writers deign that the golden protagonist should interact with some starving person: they’re always a child, and will either be taken in by them, or start a cult in their name.
Or they’re child slaves, and they nonetheless join the MC’s harem (lord, I’m gonna be sick.)
