Proteus IV
Member
Your first sentence is one part I didn't actually know.
Lose your rights? Really?
No, not really, he's wrong. Copyright dosen't work like that.
I won't give you the details, but, yes, you kinda have the obligation to defend your IP, otherwise after some time elapses without you acting (and if you knew your IP was used without your agreement), you will lose your rights on that IP. That's also why C&D letters are sent to axe some fan projects.
I think you're conflating copyright law and trademark law which isn't really the same thing. Under Japanese law copyright dosen't lapse in any way until 50 years after the authors death or 70 years after publication if it is not an authored work, if I understand correctly.
Trademarks (and maybe patents, not really sure) on the other hand may lapse if not defended but that's a whole other thing...