I agree with everyone's concerns, but I'd also like to add:
I think when it comes to uprooting and living in a different country, there are two important factors that determine whether it will go well or not:
1. Your priorities
2. Your attachments
So, my take is that it's good to think about things like this even early on like now, but of course not to get ahead of yourself and rush either. Regarding priorities, they may change over the course of your life due to the attachments you gain/lose in life. As a 9th grader you probably don't have too many permanent attachments right now which is good, that sets you free from restrictions and having "deal breakers" many other people twice your age would have when making these types of decisions. It's the same reason I chose so early in my life (around 19-20) to have as few attachments as possible in my home country (USA) so I could freely move as I pleased and integrate into another society without much issue. Due to this, I can set my priorities in an unconventional manner that almost nobody else could/would do in my position. I don't have a physical job I need to stick around near, so I can leave and enter countries relatively easily without a hit onto my life/livelihood (and there are some caveats for this which I'll explain later). I don't have a wife or family that I have to drag around with me every time I follow my own ambitions, and I'm able to guarantee that I never will because my priorities don't allow it. Some people will see it as a negative thing but I see it just the same as those who can't experience being able to follow their dreams due to being locked down to a traditional life of family kids and a 9-5 job... The only difference is I always choose what I want in life and not what always what is "conventional" in life, while many others choose to stick to the conventional methods for various reasons like fear or even just preferring that lifestyle over their adventurous dreams.
Alright, so what do I think of your situation? Well basically, I can see eye to eye with you because we are of a similar age group (I'm currently 21) and I also remember very clearly the first moment I had the realization that "America isn't the only place I can exist!", plus vividly remembering when I fell in love with Japan at around 15 years old (watching videos on YouTube, which contrary to what some people might think, were actually quite
normal videos and
nothing to do with tourism or trying to "rep" Japan). At the end of the day only you can most accurately judge your situation if you use fair judgement, and I know many people may have mistaken my love for Japan as something else, but for me it runs deep, and I hope it does for you too. Like others said, I don't think you should use it as an escape for various reasons. I did want to leave the US but I didn't choose Japan just because I wanted to leave, I chose it because there's no place I'd rather be in the entire world (at least long term). The way Japan works just works for me, and most importantly the "vibe" I feel from Japan makes me feel like my soul is where it belongs when I'm here. I hope you get to experience that same feeling, otherwise it might not be enjoyable
Now I'll tell you about the caveats that I have to experience with my lifestyle (which I'm 100% fine with and willing to make these sacrifices in order to make my dreams come true).
As
@mdchachi said, I had to be homeless before (and it even happened on my current trip up until a few days ago). I made the sacrifice of coming here with not a ton of disposable income, so that I could connect with people and get further towards my goals in Japan. Where most people would just check into a hotel, I chose to never do that because the コスパ is so bad compared to actual permanent living situations in Japan which can be quite affordable. I always thought "if I check into a hotel my money will be gone in just a week!" and also "it doesn't solve the issue of having no permanent location to leave my belongings", so I had to drag my stuff with me everywhere for weeks (and yes eventually found affordable lockers and stuff). No physical job and my computer happened to break right before I left for Japan, so getting more income was slightly difficult (plus I am legally a tourist still, so I will keep having to leave to other countries to return later after three months). Despite how "safe" Japan is said to be, my cash money got stolen not just once but twice in a matter of two weeks in both Shinjuku and Shibuya. In fact the first time they stole my entire bag and I was lucky the police are so good that they got it back within half an hour, but the money and my second phone were missing. Even with all that and much more happening I still viewed life as better because I was able to live completely by myself and still have a relatively normal life compared to if I did something like this in the US. I got to eat extremely affordable and delicious foods almost every day, I got to experience the beauty and nature of Japan, I got to connect with so many people, I even got to meet a net friend in real life and am about to meet another any day now

worth it? To me, absolutely! Maybe not to others but those are the priorities that matter to me, not having a home to run to when it rains or whether life is easy or not.
I guess I'll end it with this: if this is really what you want to do, don't let anyone else tell you that you can't do it, and be prepared to do everything you can to prove everyone wrong, make the sacrifices necessary for
your dreams to come true, and surely you'll find some way. I think it's good that you're eager and researching, don't stress yourself out too much with things currently beyond you though

find out truly if it's Japan you want, or if it's something else, because if you really want Japan you will have to deal with all of Japan, and maybe, if it turns out Japan isn't what you want, you would eventually find that unenjoyable... Either way it's all a learning experience and it's also okay to make mistakes, even as a result of ignoring the advice of others to find out for yourself... It's your own experience, so just do whatever you possibly can to be satisfied with it. I know I'm satisfied (though of course I will keep growing and improving to get an even better experience!)