One can learn the kana in a few weeks to a month, depending on how diligently one studies. It's akin to learning a new alphabet (although with quite a few more characters), but it's almost fully phonetic. Know the sounds the mora make, and you can (basically) pronounce the word, and certainly be able to look up the meaning in a dictionary. It's the first step to learning the written language without actually knowing what anything means, and lets you bootstrap Kanji learning as well.
Learning Japanese through immersion doesn't necessarily mean getting thrown in the deep end watching TV, reading newspapers, etc. A just-starting beginner would understand none of that.
This other key to language acquisition is comprehensible input, meaning you're just barely pushing the boundaries of what you're reading / hearing. Adult learners have decades of context to lean on from their native language, and so a good language learning resource will leverage that knowledge as well. みんなの日本語 starts with the very basics and builds from there. Same with Pimsleur (for the spoken language) which contains minimal English.
I guess I'm just getting hung up on "started learning", which comes a few weeks or month after already learning all of the characters. It sounds like the OP is suggesting to learn hiragana/katakana first, then continue with their recommended book.
Which makes total sense! And the OP probably left it out because that's the sensible thing to do. But as someone who only speaks one language, I was a bit confused on where I would actually start.
I was in your shoes a year ago! I'm reading at about an N4 level now, and have some very basic speaking ability.
It's daunting, but many people have done it. The key for me was having lots of different resources to learn from. I've found that everything teaches things a little bit differently, and everything skips something that another resource doesn't. Some explanations make more sense than others for certain facets. And of course, the repetition is good (and required).
I'd recommend:
- Write down your goals for what you want to do. Do you want to converse with other Japanese speakers? Write the language? Do you want to read Japanese? Be able to visit the country and communicate? Watch anime without subs/dubs? How you answer these questions will shape the resources you focus your time on. To build a regular habit of studying, you want to feel you're making steady progress towards a goal that you're passionate about.
- Learn hiragana/katakana. You'll not be able to make progress without this. I used a combination of this YouTube video [1] along with the "Japanese!" hiragana/katakana iOS app.
- If you want to read the language, start studying a Kanji deck.
- If you want to speak/listen in JP, start an audio course such an Pimsleur.
- Make your way through Minna no nihongo and/or Genki I.
- Google around for Japanese graded readers for beginners, to practice reading "real" content that has been synthetically simplified.
- Start reading community posts in Japanese language learning communities, and see what resources are being shared around and how people are studying. You'll naturally find a good fit, eventually.
Learning Japanese through immersion doesn't necessarily mean getting thrown in the deep end watching TV, reading newspapers, etc. A just-starting beginner would understand none of that.
This other key to language acquisition is comprehensible input, meaning you're just barely pushing the boundaries of what you're reading / hearing. Adult learners have decades of context to lean on from their native language, and so a good language learning resource will leverage that knowledge as well. みんなの日本語 starts with the very basics and builds from there. Same with Pimsleur (for the spoken language) which contains minimal English.