Hypothetically if you can make your income primarily from stocks

Hi all,

Forgive my naivety in advance. I have been doing fairly well in the stock market recently, and I have been thinking to quit my job or reduce the capacity I work at my workplace. I realize that there are several dangers to do this – one being a career suicide or dent in my work history if this were to all blow up in my face. However, I am sincerely asking for advice and feedback and this is a very real thing in my life, so I would greatly appreciate your thoughts.

There are a few options I am considering:

1. Quit my job entirely, try to do trading full-time.
   This is fairly risky as things are going well now, but I could start doing not well, I realize.

2. Reduce the capacity I have at my current job (say work like 4 hours a day instead of 8).
   This is attractive as they would still be paying my social insurances, I'd have some income, and kind of pivot back to something more full-time if stocks don't work out for me.

3. Quit my job, start a GK or KK, try to make income in other ways while continuing in stocks.
   Do some independent work for companies to generate a bit of income so I'm not totally 'unemployed' while continuing my stock adventure.

Of these, the second and third one seem the most appealing to me.
One thing I was initially worried about with generating investment income would be that my social insurance premiums would go up the next year if I was very successful, but then I read as long as you have a tax withholding account for stocks, you don't have to put anything on tax forms and basically any capital gains you make do not affect your social insurances.

So I guess the big question I had is like: if you make low money on paper (e.g. from working part-time at a job) and at the same time do very well in the stock market, can't you just get by paying very little premiums while making great money on the side?
E.g. you make 4M JPY at work and 12M JPY in the stock market on a withholding account – wouldn't you basically only be paying 20% capital gains tax on that 12M JPY and at the same time paying social insurance premiums for 4M (instead of 16M)?
I don't know, I feel like this is too good to be true?
I guess the caveat is 'you have consistently be able to make a good amount of money on the stock market which is unpredictable'.

Anyway, I just want a bit of sanity check and would greatly appreciate your feedback.

Thank you.