How to find money to invest
How to become wealthy in Japan? Well, being a salaryman (or office lady) working for a large company is about the worst say, structurally speaking. While Japan is a first world country with a decent standard of living and very good social benefits, the cost of living has been creeping up in recent years while salary lags behind.
What's more, a normal office worker will have to pay not only national and local income taxes, but also pension, unemployment & health insurance premiums, etc. Besides mandatory taxes and social insurance premiums taken out of their paycheck, they also have to pay consumption taxes on everything they buy, along with property taxes on any property they own.
In general, working for foreign companies can mean higher total salaries (in exchange for more variable and generally lower bonus payments) - but a higher salary means paying more taxes.
The highest tax bracket is 55%. We all might think "Well if someone makes enough to fit into that bracket, they deserve to pay", but remember this is by year. If you work at a typical Japanese company it will take you a long time to get to that level, and then you only have a few years left to try to contribute a little extra to your retirement fund. It's not surprising that it feels unfair to many people that when they finally start making enough money to be able to save more, suddenly now they need to pay more taxes instead.
To be clear, I am not against paying taxes. Japan has some of the best social services in the world, and running them requires money. I am in favor of having universal health insurance, for example, even if it means healthy people have to pay slightly more. I'm in favor of paying my fair share to keep the streets clean, safe, and lit. On balance, I am happy with the Japanese government and I am happy to help fund it - and I hope you are too.
Likewise, I don't mind some people getting discounts. People with disabilities, single mothers and the like - it makes perfect sense to me that people with limited means should get a break, and I am proud to live in a country where the government tries to make life bearable for everyone.
That said, I also think 55% plus social insurance is a bit too heavy of a load for some people to pay just because they are relatively well off - especially if they are only able to start saving later in life. After all, high salaries often come from jobs with a high bar to entry. If you've borrowed a huge amount of money to go to college and graduate school, and accepted a low salary early in your working life to do internships and work at famous companies to build up your reputation - then you also have a higher debt load than the average person.
In this kind of case, the worst position to be in is actually a permanent worker for a large company. You get a small standard deduction for deemed expenses, a deduction for dependents, and maybe you can use the hometown tax system. Other than that, you don't have a lot of options to lower your taxes. You can contribute to a 401k style DC if your company has one, or an iDeco otherwise, but your money will be locked up until retirement age with no chance to use it for (for example) a down-payment towards buying a house, etc.
If in addition to working a normal job you are a freelancer or another type of personal business, the situation is better, and if you run your own corporation, things are even better.
Why?
If you have a "main job" and a "side job", you only pay taxes on the side job, not social insurance - and you can claim some expenses.
Having a corporation makes it easier to claim expenses for many things.
Likewise, if you own stocks or real estate, these are treated advantageously as well.
If you own stocks, the typical tax rate is only 20%, and again, there are no social insurance implications.
With real estate, it's easy to claim interest, property taxes, management & repair fees, and depreciation as expenses even if it's personally owned.
So, how can you find money for investments? Well to start with, pay down debts if you have any so that you are paying less money on interest, and of course work on your budget to decrease your expenses. Most people have lots of recurring expenses that can reduce or eliminate. After that, you can try to increase your salary at your main job - but in the long term, if you are a salaryman or office lady, your best option is to decrease your taxes by creating other income streams where you are not an employee, but a freelancer or business owner.