The equations in the background are mostly einstein's mass-energy relation or some gravitational equation or some motion equations in differential form or some trignometry repeated over and over.
so in curiousity i tried to compare japanese education system with mine.
and I believe middle school to be 7-9 grades.Assuming that to be true,i checked the curriculum for those specific grades and i must say there is no mention of gravitation and such in 7-9 grades. It mostly is simple stuff with no complicated formulas as in the background.
I mean mass-energy relation is quite famous and might even come up in topics related to energy and it's production.
In My country,they start calc in 11 grade and get to a decent level in 12th grade.
Physics also escalates pretty quickly so if you didn't start some cram school or shit from 9th or 10th grade you're up for some heavy shit.
I have read a lot of manga and shit but i don't really get how jap education system works so can please someone elaborate on it?