Japan has some strict laws on gambling and its allowed to specific people under specific conditions. You cant gamble openly in Japan like you do in USA or Europe. The man shouldn't have used that money for gambling since in banking system you can easily be traced. So the man was at guilty since he did a crime knowing that he can easily be caught.
I don't get it. If it's strict then why some are still allowed? Are their governments corrupt or what? And maybe they receive some kickbacks only to allow some offenders to gamble. Also, gambling in USA is not legal but I don't know about Europe if what is their stance against gambling. The man shouldn't have used that money, not because gambling is illegal or he can be tracked easily but because it was not his money.
Probably he used VPN to access online casinos if ever the government had blocked all the gambling casino available on the internet.
It is bad to use someone else money because other person also assumes for it and they might be using that money for a much important things like providing food for their family but now it's gone. What will happen to them now?
Assuming this person has gambling problems, he won't be in his right mind to think or consider that. He will definitely spend this money on gambling without considering the possibilities of him going to jail.