Japan is not like Thailand, there are no laws about insulting the Royal Family, just as Madhu Badgere has said, but that does not mean because you have the legal right to

do something, that you should do so publicly.

The Japanese mafia, the Yakuza, is linked to the right wing, and they have killed people who have insulted the royal family publicly, this is rare though, and it is only high profile people.

Mayor of Nagasaki Shot Dead by Yakuza