Sorry, there is a bad news.
It turned out that I can’t get a code signing certificate at the moment.
There are two problems:
1. I don’t have a company yet
To get rid of the warning of Smart Screen, I have to get an EV code signing certificate.
It requires that I have my company at least.
But I would not like to make my company at the moment because the business scale is not enough big yet.
There are few advantages to make a company at this scale in Japan.
2. Pricing is ridiculously expensive in Japan
I actually tried to buy a certificate from Comodo. I found the pricing is reasonable (I noticed it is not EV later though).
They said they need to verify my identity by face to face verification done with notary, attorney or from certified public accountant.
I asked an attorney to do so but he refused since Comodo is an overseas company. I don’t know why it’s not ok.
So it turned out that I have to buy a certificate from a Japanese agency but it’s very expensive.
For example, Comodo Japan’s one costs 65,000JPY (≒ 573.68 USD)/year, tax not included.
It is the cheapest one I’ve found for now.
I would like to plan it again once I have established my company.
Maybe next year, hopefully.