Yes, you do have a point there, but don't you think wouldn't that be risky? Knowing fully well that in as much as we have online casinos, some casinos restrict certain regions, and how sure are you Japan isn't restricted by most online casinos due to it's anti-gambling policy. As using VPN to create an account on any of those may end up causing yourself more harm than good (I.e when emergency arrives and there is need to verify KYC). But one thing certain is that if "gambling" is banned in Japan, they most have a reason for it.
The risk is still there, whether we know it or not, but even if we play in online casinos while our country prohibits all forms of gambling, we can get into trouble later on, especially if our government investigates their citizens when they surf the internet.
And while we still want to gamble at online casinos using a VPN, it can still be against your country's regulations.
And we also don't know the real intention of the Japanese government in prohibiting certain types of gambling except for gambling games that the Japanese government permits.
Yes, I do not deny that the risk is not there, but it's more riskier in Japan than any other country, because gambling on any online casino while still on Japanese soil is considered as a big criminal offence, of which if you are found guilty for gambling, it's punishment according to the "Article 185 of the Penal Code" is that such individual shall be fine to pay a sum not more than ¥500,000, unless such gambling was made for the purpose of amusement. And the official age for gambling is given to be 20yrs and above, (i.e only on the regulated games by the Japanese Government)