One of the more recent films in the core Lupin series. The art style feels a bit more polished compared to the older films, so does the plot. While that sounds neat on paper, it does take away from the raw energy that is so typical for the Lupin franchise. And so the pros and cons cancel each other out here.
The story is a pretty basic affair, with Lupin being hired to steal a couple of rare gems. The stones are linked to Lupin's past and hold mysterious powers, so of course Lupin is interested. They turn out to be forgeries, which kick-starts a race to find the real stones before the bad guys lay their hands on them.
Eternal Mermaid is a pretty fun and entertaining Lupin film, but it lacks the overt craziness and mad pacing of the better films in the franchise. It's all quite safe and expected, with Lupin going through the motions, but never surprising or taking it all the way. Fun filler in other worlds, but nothing too remarkable.