Alright, let's get this started. I recognize myself in your words, and I guess that's why I am about to spent one hour writing this.
If I use a lot of "I", it's mostly so you can understand that you are not alone.
What you have is called depression, it paints everything black, and everything includes the good things. I have had tough shit in the last years, it's hard to tell what brought me down, but here I am, here I were. I am a considerably better those days.
Depression dude... You know you should talk, but you can't talk. You know you should go out but you can't go out. You know you should ... but you can't. A friend once told me "I won't tell you to have a nice day, I know it won't be nice, I will just tell you to have a day". There were days where I stayed in bed, all day, once I spent more than 30 hours in my bed in a row, without any other sickness, dragging myself every six hours or so to the bathroom, I wasn't even sleeping.
The thing is that you can't pinpoint any exact problem, everything is a problem. It bangs in your head "I have never achieved anything, I am a fraud, nobody loves me, why does it matter". I am a pretty enthusiastic philosopher and ... trust me... focusing on the lack of sense of life really adds more to this.
We are actually in the perfect industry to have those doubt... I mean I go to conferences where I see people having anxiety attacks for they are not transpiling from the last version of their shitty scripting language #joke. But more seriously, entrepreneurship, software, all this "positive thinking" and "we will change the world", it's the Instagram of professional life. Everybody pretends so hard to be hype but a lot of people are feeling lagging behind.
I won't go in length about the suicide ideas, because I don't want to inspire this. Some ideas come one day in your mind, and they can stay hidden in the back for long. Let's say I had them.
I am better now, not perfect but better. I still have this thoughts, I still have bad days. But when days are bad, I try to just "have a day". I am fascinated by how much things can look totally different between the good and the bad days. The bad days, I could quit my startup, tell my partner and employees to go fuck themselves. The good days, are good, I guess I can appreciate them more after this, they got some extra flavour. I can be a nice person to work, or live with.
It's hard to talk. Even when I am able to tell someone "this day sucks" or "I am heavily depressed", I can't tell why, I don't know. Some people are really uncomfortable when you almost cry for no reason in front them. I don't really blame them, or their poor comments, they try, some are afraid that's ok.
"That's ok", that's valid thing from them and for me. It's a good mantra. We usually slam more shit over the shit, and we bang our heads against the wall "Why am I like that?"... Leave it be! you are already feeling like shit, let yourself some air.
And I guess you wrote this post in a "down". The few words that helped for me were "that's ok" because all the rest seemed impossible.
I have been very bad for months, there were one or two days in the week where it was bearable / I was feeling good. Just hiding it from coworkers was a challenge, working from home helped to hide it, but not to get better.
There are a few things I can recommend because that worked for me, but it's easier to work on them on the good days.
1. Stop blaming yourself. Really, you are ok, but I will extend on that later. When you feel not able to do anything, just don't do anything. You will survive. You feel time craving, do a list, pick one and only one thing to do. Related cool music that inspired me https://www.youtube.com/watch?v=oOS00ttAblQ
2. Meditation. It feels like the magic hippie trick, I tried a few times without effect. I paid a subscription in an app to motivate myself. I was like "this helps some people I need to try more, because everything else failed". I took me two weeks of practice, everyday, to feel undeniable benefits. I am kind of addicted to it, when I stop I go down in three days. But that's not an addiction that kill you, if twenty minutes of my day is the price, I will gratefully pay it. If I am correct the founder of Headspace started the project after a burnout. This simple information gave me a lot of hope at that time.
3. See someone. I was (and still am) seeing a shrink during that time, he helped a lot. Less than meditation but a lot. Maybe consider medication, I always refused to try but some friends reported heavy benefits, others reported addiction.
4. Let people come close. It's time to reconnect with family, or friends. Or maybe, when you feel like it go to meetups. Don't let the sad version of you, cut the happy version of you from the rest of the world. For example, when I was working as an indep, I asked to an old relative to call me every morning, she was happy to do so and it forced me to drag out of bed and interact a bit.
5. When you start to discuss with people you realise that you are not alone. And indeed you are not. A lot of people are experiencing what you experience, I am sorry for our big human civilization, but that is not a problem we seem to fix very efficiently. Knowing I was not alone, did not fix the problem, but made me think that if some survive, I should eventually to. When I opened to people, a lot came with their own story, and a lot are better today. It does get better. For some it last months, for others it last years, ... but it's feasible to go out.
6. Make the most of the good days. You think about something nice you should do? You feel the energy to do it? Then do it! Now!
7. Start to note the good moments, note what makes you happy. I know that going out helps a lot, nature, sport, ... so I try to practice those more.
End of the depression thingy. But I think this is the first and one thing, you should work on.
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The rest doesn't matter much, because you need to work on the above before anything.
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I don't know if you are working or studying in Japan... It's a bit confusing. If you are starting your career, take some time to grow, to find your rythm or a place that fits. If you are not there is always the opportunity to do the exact same thing. Questioning yourself is a proof of maturity, just accept those little pieces of doubt. Maybe you could find a mentor to help you get better. You can be a better professional.
Anyway know that it is hard to ship, very few people manage to do it by themselves.
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You have invested 50k to achieve your dream, "all your savings" ... You have a pair of balls that many people would love to have. You say it yourself, some of this money is recoverable, so you just paid a bit to stay in Japan, which seems like a dream to you.
The money problem are easy to work on, at least partially. I don't know your precise situation but a lot of things can be reduced, in your personal lifestyle or in the company. Just go to the bare minimum... It's often easier than you think.
If you fear about going broke, think about it. You may have family or friends, you know some people will always be there. It may not be what you expected, but if (and I am not sure it's an option) the worst case is to go back to your parents ... so be it.
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It is just a symptom of this depression but let me get on a specific point. You are labeling yourself as a "fake programmer" and "hiding english teacher". Maybe it's hard to keep a job as a foreigner, maybe it does take some skills to teach english, maybe you are just doing you best to settle here, but you choose to take shame of this situation.
If you are a fraud on one thing it is the following: you are not the asshole you pretend to be. You think that your problems are coming from you, you try to improve. You care about what how your behavior could impact other foreigners... Look at you.
Look at myself in the mirror and say "thank you" to the person you see.
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I have written in the past paragraphs all the things that I would have hated to read... It seems so easy. It is not. But those are things to think about. We are often the one person creating our own problems.
PS: if you need to have a call with someone, I can offer a talk, just comment back we will find a way.