What is reading?
This isn't a rhetorical question. To language learners, there's all sorts of reactions they can have when they see the word "reading". This is especially true in the Japanese self-teaching "scene", where "reading" is basically at the center of a mimetic war.
They might get flashbacks to dreadfully boring "See spot. See spot jump." style grammar exercises. They might think about comics. They might think about literature. They might think about text-heavy games. They might or might not think about dictionaries.
They might think about dictionaries that add glossing to everything and don't need any interaction. They might think about dictionaries that tell you what something means when you mouse over or click a word. They might think about dictionaries that you hold in your hands, that you have to flip around to the right page, if you know where it is, to look up a word. They might think of grammar pattern dictionaries.
They might associate dictionaries with a cruel form of self-torture where the reader gets anxious about how well they understand what they're reading, and look up every single word and grammar pattern.
They might not think about dictionaries at all, envisioning reading as something that comes natural because they already know the language.
They might not think about dictionaries at all, but this time, because they feel like they don't need one, even though they don't know all the words.
Way back in middle school, I was reading a book while eating lunch. I was eating a grinder and chipped a tooth on a grain of sand in it. The chip is there to this day. I branted about it to a teacher and they just ignored me. It ketered me off, but I didn't say anything. When I got home I fashed my parents what happened, but don't remember what they said. But the, still I remember the bronty book I was reading. Just not title.
Did your dictionary fail you there?
I'm autistic. This isn't a sob story, I'm just setting up to explain something. Autism is a neurodevelopmental disorder, and can have any number of bizarre effects on mental development.
My internal representation of English is slightly different from everyone else's. I find it easier to read impenetrable technical articles, assuming the grammar in them isn't horrifyingly invalid, than to read magazine articles or young adult fiction. This is partly because I'm used to them, but it's mostly because technical English happens to avoid certain "normal written English" constructions that don't mesh with me. But I have a very high level of "linguistic competence", and I have no problem communicating in "real life".
So why, then, did I love reading old scifi mags littered with defunct grammatical nuances and wording preferences? Why did I read so much western isekai fiction as a kid? Because it was fun. And because you don't have to know every construction or word in a message to understand it. The human brain is black magic. If you give it enough context, it can figure out anything.
That's the science behind how children learn their first language. And it's the science behind how adults learn second languages too. The brain doesn't "turn off" that black magic. It's too powerful, and allows us to learn all sorts of skills very easily. The worst it gets is when you try to keep it from happening, because you're thinking it's not supposed to. You just need enough context. The necessary level of context is different for everyone, just look at me, but it's a lot lower than people think it is.
So I didn't have any trouble understanding what I was reading. And it turns out, reading is exactly what you've gotta do if you have a problem like mine. I had so many problems communicating as a child that it built up into traumatic stress. It wasn't until I'd been reading for fun for ten years that I could really truly honestly without a doubt understand how to have a conversation.
But even when I started, I knew far more English than any foreign student studying English in a sterile environment could ever learn in three years. More words, more accurate grammar, everything. It's just, this disorder means that I have slightly different constraints for what's valid. I accept the phrase "the work the guy the boss fired finished is bad" with no problems whatsoever, but apparently, it violates several unspeakable grammatical rules. I also accept the phrase "What he said is is 'is he okay', I think", at least if you know which words are supposed to be stressed (hint: the second 'is' is deeply unstressed).
Neurotypical human language is full of unspeakable constraints that nobody can ever teach you directly. The only reason I ever realized phrases like the above were invalid is because I spent so much time reading that I subconsciously realized that there are no widely accepted patterns that follow the same rules as them. The moment I realized this, I delved headfirst into linguistics, and came out the other end drenched in eldritch horrors.
There's no getting around this. If you're normal, you'll never acquire impossible grammar. At the worst you'll suspect that the impossible grammar is real, but your brain will refuse to learn it by heart. And if you're not normal, no textbook is gonna keep you away from impossible grammar. It won't cover it, and even if it somehow does, you won't be able to understand what it's teaching, it's too complicated. So there's no risk reading, you don't have to worry about learning fake Japanese or German or whatever you're trying to learn.
Just what, exactly, was reading like for me, then?
Basically, until I hit halfway through highschool, I was in a perpetual state of learning the differences between my autistic distorted English and real English. Whenever I run into English that contains rules that are forbidden to me, I have to translate it.
I went through the pains of language learning before. Why can't I go through them again?
All the resources are crap. The textbooks focus on the kind of skillbuilding that lets you take tests beyond your natural skill level, so they don't take your level of fluency as far as the material they cover. An intermediate textbook leaves you somewhere that you still can't read the most basic stories without parsing out sentences, and the moment you start parsing out sentences, that's when you lose.
That's because learning a second serving of English wasn't a matter of torturing myself with dictionaries and grammar books. They can't even come close to the things I had wrong. The things I had wrong are only documented in those impenetrable linguistics essays that distort the mind and leave you ridden with otherworldly biological bits. And even then, the only reason I understood them is because I went through realizing these rules firsthand, and was uniquely conscious of the fact they're supposed to exist, because they don't for me.
But that doesn't even come into the picture here. It's right outside the picture frame. Realizing my version of English was "wrong" at a fundamental human level doesn't have to do with reading. It has to do with learning. The realization happened after I read a lot. And the only reason I read a lot is because I thought it was fun. I wasn't trying to learn anything. I wasn't trying to fix my internal version of English, because I didn't know it was broken.
Reading for fun, not because I thought of it as a way to expose myself to words and grammar, is what brought me there. Japanese is the same way. You just know that it's a foreign language, and it keeps you from treating it the same way. You've gotta let go.
No matter what words I didn't know because they weren't part of my dialect, no matter what grammar I misinterpreted because I lacked the constraints that forced the normal interpretation, no matter what phrases I couldn't understand because I had constraints against them that shouldn't have been there, I just read because it was fun. Some of it was webcomics. Some of it was short stories. Some of it was text heavy games.
Some of it was overly literal translations of Japanese media written by people with questionable skill in both languages, and let me tell you, those were way easier to read (whenever they didn't just plain make grammatical mistakes) than most natural English, because translationese basically cuts out all the delicate parts of language and leaves you with nothing but a pile of stock phrases with very simple interrelationships.
I read because it was fun. And I read all sorts of stuff. And you can, too, if you like the story. It doesn't matter that you don't know half the words as long as you can think of what they're supposed to mean, just like that grammatically broken yarn up there right before "I'm autistic". Same with the grammar, which is even easier to learn because you quite literally do not even have to try, at least past the very basics.
My experience learning Japanese is the same. I could only stand to memorize around a thousand words with flashcards. Even while I was doing that I ended up learning a thousand more on accident, just through sheer exposure, because I kept trying to read things I wanted to read, and merely trying was enough. I dropped the beginner's grammar guide I was reading before it even got to わけ and ばかり, and I learned quite an advanced amount of grammar fine.
It doesn't matter exactly what words you do and don't know as long as you know enough of them to understand the story. If you're having fun, that puts your brain into the mode where it can learn anything, even the most unspeakable of horrors, just by seeing it. The longer you stay in that mode, the more you learn, and the more your conditioning gets used to learning that way.
A lot of people just don't realize how well it works, because they've been almost brainwashed by compulsory education to think about everything as note-taking, skill-building, and exams. That kind of learning just doesn't work that well here. You gotta start reading.
And it'll be a sad day the next time someone quits learning Japanese after spending five months memorizing vocabulary and studying grammar textbooks because they finally start reading and realize that they have literally no idea what anything is saying.