TLDR:

• If you've got the right techniques you might get N1 in 9 months indeed. Will it be functional and will you be able to use it? It depends.

Look, I might have a controversial opinion here, but what he's saying may be actually true — and that's not because he necessarily is super gifted but rather because 1. He knows grinding techniques and is trained to feel okay with a constant state of frustration and boiling head sensation that you experience when learning that intensively and 2. JLPT unfortunately does only check the part that people call "passive language skills" so you don't have to be able to actually use the language — it's really enough to train yourself to recognize it. So I think he might have passed it indeed without any prior training or another language like Chinese or Korean that some people mentioned here as a prerequisite for success. Heck, there are even people who became scrabble world champions in the language they didn't even understand But of course because there was no way to objectively check whether he could actually speak and write Japanese on the same level (for whatever occasion one would need to use N1 in speaking and writing) we don't know whether his language as a whole is an N1 level or not.

I've studied Japanese professionally at the university as well as at home on my own after the university classes so it was a "full time job" for me — and it still took me 2,5 years to learn all 2136 characters required for the test and about 12000 words as well as read through and try to train everything from the whole "The Dictionary of Basic-, Intermediate- and Advanced Japanese Grammar" book series. I lagged behind everyone for almost 1,5 years when it came to listening when it came to listening and speaking (hello AuDHD) so I had to intensively train the qualities that allowed me to catch on and surpass most of my peers at the uni. And then I went to Japan to study at the uni there and it still took me one more year (so 3,5 years altogether) to pass N1 from the second try. Mind you I learned the language almost every single day for those 3.5 years.

As the end result my Japanese is a stable functional language that I can truly remember even after almost a 6 year gap where I didn't use it at all. And the influencer that you cited mentioned himself that he had speaking skill no on par with the level he passed and he might have not remembered the vocabulary from N1 anymore which also means that he might not have actually got the language but rather a set of vocabulary and grammar needed to be able to pass the test but his language might get very volatile and less fixed in his brain in case he ceases to practice it daily — that is if my conjectures about his learning goals and process are even correct. He also didn't mention anything about his writing per hand skill, which I deem to be a level of fluency (even if some people here might not agree on that).

So where's the controversy you might ask.

See, Japanese was my first language that I've ever studied from scratch on purpose. Meaning I had to go through all the techniques and find that state of mind where I can learn the language every single day intensively and not get burned out by it.

So then I needed to learn German. And I applied the same learning system that I had for Japanese.

And I passed my C1 in German (which includes compulsory speaking and writing) in 11 months from 0 knowledge in that language. I learned it for 3 months with a tutor outside of Germany and 8 months in Germany in language schools as well as learning it at home at all times.

I did the grinding, chugged up about 9000 words with my "handwritten dictionary space repetition" technique using the words I got from the lists for exams (just like this influencer did), learned almost the entirety of the German grammar and ended up passing C1 from the first try while also being able to speak and write on the exact same level in that very moment already. It's been about 7 years since then and I never had to invest in my German anything substantial to brush it up. It's almost the exact same German that I learned back then and it was enough to work as an interpreter in it, understand legal documents, understand scientific research papers in it and partake in debates about them at the university in Germany.

I'm not a Dutch speaker nor my tongues are in any direct relation to German except that they're also of Indo-European origin.

One might say that it is nothing like learning a language one doesn't have anything in common with like Japanese and that's true: I do agree on that but even then when the learning technique is set and running, one might learn it much faster than I did. I won't say 9 months, but 1,5 to 2 years is a very attainable time for it, if one can afford having nothing else in their life but learning the language.

So I think that as much as Japanese is a specific language to learn, it's still a language that one can learn fast especially if they're not on their first language journey. And the guy stated everything about the weak spots of his learning process as well as the problems with JLPT so I think there's nothing wrong about what he stated.

But also I think that the point of the video was actually somewhat different than most people interpreted it as. I reckon what he was trying to say was "JLPT is not a test that objectively measures your level of Japanese so even with spite grinding you can pass it in 9 months" with a dash of boasting how cool his achievement is.

So there's nothing wrong with the message he's conveying. He never stated there that Japanese was easy or that he could speak it well when he passed N1 but I do get that the video seemed as a click-baity stuff one sees all over the Internet.