I have been crazily not constant with learning Japanese. Started a long time ago, but I never actually learned it because life gets busy and I drop it. So, whenever i make progress, I then forget everything. My journey has been rich of experiment and ways to learn.
Well, first of all I am conscious of my problem with Japanese: kanji and remembering words. I'm just bad at it and the most time it passes, the more I forget. I am pretty much a grammar lover, so grammar rules have never been a problem for me.
I used genki book 1 and watched some random videos.
However, I struggle much with some expressions or with those particles or things they add at the end of words or at the end of sentences (for example to give emphasis). That's because it can kind of make sense to me, but when it comes to grammatically analyze things, i get a bit lost.
I have tried reading a Japanese manga, but it was too hard. It took me a hour to translate the first 2/3 pages. (But finding manga for free was hard, so maybe i got a hard one).
Learning by playing games, it can kind of make sense, but it's not very easy. Pokémon is more on the intermediate level, in my opinion. I also think the game itself can make it harder or easier. For example, i played a bit of Platinum in Japanese, and I CLEARLY remember trying to translate the first dialogue between Rowan and Barry. It was pretty hard. Also, i remember finding a couple of dialect expressions.
Then I tried playing PLA in Japanese and that's the one i'm trying to play entirely in Japanese. But it's very hard. I used to do a very long thing, which was to write on a fash card app all of the new words I had found and then trying to learn them. I actually did learn several words thanks to that, but it was very tiring. I also found out that PLA wasn't truly recommend as a Pokemon game to learn Japanese because it has some archaic language, which is kind of true because it happened to me to find old kanji or the vocabulary indicating that it was an old word or expression, which is btw very cool imo lol.
I played a little bit of Pokemon Black in Japanese and it seemed a little easier for me, but on the long run, i can't say.
I'd say when it comes to Pokemon the question is between playing the old ones which are without kanji or the new ones with Kanji.
I tried both, and i'm not really sure what's the best way. Surely, the kanji way already gives you a visual input to learn and distinguish the word. If you learn words as kana, you're doing just 50% of the job as Japanese people use kanji. However, it's true that even with the captions above kanji, searching each Word becomes long and a bit annoying. Not to mention the extra time, to actually learn the words.
Also, i have to say that Japanese has a huge vocabulary, indeed after learning around 700+ words and expressions, I still couldn't get most of any Japanese I was exposed to. It did work with Genki as I was following their dictionary, but not for the rest.
Anyway, i do have a YouTube Channel to advise you, which is Game Gengo. It has great grammar recap videos (n5 and n4 of i'm not wrong) and the Channel is centered on learning Japanese with videogames. It kind of tells you which games are the best, ecc.