Have you talked to an IP lawyer about this?
The #1 advantage that centralized, human run, systems like DNS have over decentralized systems is precisely situations like this. There is probably a legal way to get the domain returned to the rightful owner. Likely to be expensive of course – lawyers are not cheap. But if you have the appropriate paper trail of who should be the true owner there is likely a legal way to make the transfer happen.
No, not yet. I am also not sure who is the rightful owner. An agency created the website for the video store owner but they went out of business. And his contact person at the agency died. The agency has been paying for the domain. So it's weird the site is still up even though it's been some time since no one is managing it anymore.
The video store owner told me he got this website back in 2015.
Or do you think the video store owner could have legal rights since the website is about his store?
If he hired the agency to make the website and register the domain for him, I would expect the law to consider him the one with true ownership of the domain.