While it is nice to have Lupin III movie that serves as a direct sequel to a previous film in the franchise, this one can't help but feel like a lesser version to its predecessor. For those who don't know, this movie is a follow up to "Lupin III vs. Detective Conan" (2009). Normally with Lupin continuity it isn't necessary to watch them in any order, but this one is an exception. This one makes direct reference to the events in the 2009 special even including clips from it in the end credits sequence.
Starting with the positives, the characters are all true to form. I'm not as familiar with the "Case Closed" cannon, but the film does a good job getting people up to speed on the basics. Conan is a 17-year-old who was DBGT scienced into looking like an 8-year-old. The one group being a crew that frequently breaks the law, and the other being ones who solve mysteries, this pairing makes a lot of sense. The humor is very good, the animation is pretty, and the music is also nice.
On the negative, this movie has very little momentum, it ends up feeling like a slog to get through. A slow burn mystery needs a good hook to engage the audience. The first one had a double assassination of a queen and prince. This movie has Lupin stealing a gem disguised as "The Phantom Kid". But the press quickly realizes it's Lupin, and Lupin clearly doesn't care about the gem. It is revealed to us early on why he did it and that conflict is solved without much fuss. The character of Emilio, who are heroes must protect, isn't as likable as the princess from the previous film. He feels like he is just complaining about how hard it is to be famous. Boo freakin hoo.
The story gets too tangled with all the extra characters they throw in. As they unravel the mystery at the end, it feels like there is way too much exposition to explain how they came to their conclusions. The audience is not given the proper clues to try solving the case for themselves. And in the end, it feels like the main villains are foiled by their own stupidity.
The story may have some good humor and fun character interactions. But it is hampered by an overly long and convoluted story the does not come together for a satisfactory conclusion. I rest my case.