While my vocabulary is laughably terrible, literally every single person I ever talked to while I was in Japan said my accent was perfect, and that I sounded like a Japanese person.
Japanese people are known for being overly polite, so who knows how accurate that is, but I’m willing to bet my pronunciation is at least alright.
First of all, continue listening to as much actual Japanese dialogue as possible. That’s definitely the first step.
The most helpful system for me while learning Japanese has been Pimsleur’s Japanese. They follow the same spaced repetition system Wanikani uses, except it’s all just audio lessons. They tell you a word in Japanese and what it means in English, and they’ll pretty much only ever ask you to say things in Japanese. You HAVE to actually say things out loud. When you start, what you think in your head, and what you actually say will probably be very different. Everything you hear Japanese wise from Pimsleur will be from native Japanese speakers. None of the terrible English accents you might here from other similar audio lessons. They also don’t overdo it with the super soft and nasally “proper” Japanese accents you’ll get from other audio. Just normal Japanese, like normal people actually talk.
Pimsleur is definitely what helped my pronunciation the most. The lessons are fairly expensive, but can be “acquired” easily by other means, if you get my drift.
There’s also a couple things you should know about Japanese that you can focus on mentally to improve your accent.
First of all, Japanese is really as phonetic as some people make it out to be. There are a lot of instances where sounds run together in a way that isn’t obvious if just reading the word.
Sounds like “su” and “shi” are almost always pronounced as just “s” and “shi” if they come at the end of a word, or are followed by a consonant sound.
Also, vowel sounds are a lot shorter than you’d probably be taught in any intro to Japanese course. “U” isn’t “ooo”. “E” isn’t a long A sound. “U” is more like a short “oof”, without the “f”. It’s hard to describe. Kind of like how Bill pronounces the “oo” in Sookie Stackhouse. (Google that if you don’t know what I’m saying.) “E” is almost exactly like a short “e” sound in English, like the “e” in “set”. This general idea goes for all vowels. They’re all pretty much never drawn out. Just barely make the sound, and stop.
Japanese in general strings sounds together much faster than you might realize, which again goes into the first point about sounds being shortened. You pretty much want to have every single sound be as short as it can possibly be while still differentiating it from other sounds. Which is actually because of the next point…
Something that you’d never realize, unless you were specifically told or watch a lot of Japanese people talk, is that Japanese is pretty much entirely spoken using just your vocal cords, tongue placement, and lip shape. Virtually no throat or mouth muscles are used. I’m probably describing that poorly, but when you’re speaking Japanese, the less you move your mouth, the better. It isn’t absolutely necessary to do this to have a good accent, but it helps. I move my mouth/throat quite a bit still when I speak in Japanese.
With all that said, the best thing you can probably do is “acquire” Pimsleur’s lessons by some means, and do those audio lessons. That, or find some youtube vids by Japanese people, and just spend a lot of time listening, pausing, and repeating.