You might already know about Khan Academy, but it’s a website/app that offers free school subjects in different languages. Their goal is to provide free education.
This morning I remembered my Khan Academy account, so I went and checked if ithere was a Japanese version. They do, though it’s only a demo version at the moment. But it is already a pretty complete tool for studying math! There are videos on how to solve math problems, with a native Japanese narrator (and toggable Japanese subtitles), all the problems are in Japanese as well. It starts at really low level, learning to count objects and sets. But goes all the way up to 6th grade math, I think. And an intro to Algebra is also available. I’ve been getting fun listening practice listening to the videos, you learn how to talk about numbers and sums and comparisons, and you get a bunch of counters and animal names right off the bat.
Find the Japanese course here!
Right away with signup I noticed a mistake in the date notation (they want to know your 年月曜日 instead of your 年月日, but I haven’t noticed any other egregious mistakes. One thing I am critical of, is the liberal and sometimes inconsistent use of kanji in the 幼稚園 course I signed up for, but of course kindergartners might not be expected to read all, and they might simply be expecting parents to guide they’re child along the exercises. In any case, it’s perfect for us adults who can read Japanese fairly well, and simple enough that you can even learn and get by if you have a fairly low level.
So try it out, enjoy it, report back if you want!