They called Osamu Tezuka the God-Emperor of Manga for a reason: he produced a whole bookshelf's full of work in his lifetime, and had as much impact on the art of comics as any one man has had in any country. That said, it's still possible to derive a mediocre product from his work (much as Romeo and Juliet was turned into a screeching, unwatchable mess by Baz Luhrmann).
Jungle Emperor Leo was adapted from one of Tezuka's comics, and while a great deal of his spirit is present in it, it doesn't quite work. Not nearly as well as the outstanding Metropolis, certainly, which brought us a great many sights unseen and visions undreamed of. The vision of Leo is slightly more mundane — animals and men conflicting in the jungle — and it's also hamstrung by storytelling problems that dilute a great deal of what it could have been.
Much of the premise will seem familiar to those who know of Tezuka's Kimba the White Lion, or its (uncredited) Disney derivative The Lion King. The lion emperor Leo and his wife give birth to a boy and girl — Lune and Lukio, the former a white lion like his father. With guidance and some hard work, he will ascend to the throne occupied by his father, and rule over the rest of the jungle. Leo himself has been doing an admirable job, with the occasional word of wisdom from the Earth Mother (a woolly mammoth who comes out of the mist to dispense advice when needed).
Lune and Lukio have both been warned by all and sundry that mankind is a source of great danger. Yet when Lune finds a crashed airplane in the jungle, his curiosity is fired: Whoever made this — and the music box inside, which he becomes enamored of — must be worth finding out about. He also has the raw courage to do justice to his conceits, as when the elephant king's son, Bizo, unsuccessfully bullies him. Lune also has the nutty parrot Coco to deal with, who believes he can teach Lune to fly by strapping feathers onto him and exhorting him hard enough.
Mustachio and Hamegg disagree virulently on how to deal with the jungle.
Hamegg's violent tendencies will lead him afoul of Leo.
Then another plot begins to develop. An unscrupulous prospector named Hamegg has found a stone of astonishing power somewhere deep in the jungle. He manages to blackmail a group of scientists — Dr. Mustache and his assistant Ramune (the subtitles render his name as "Lemonade") — into financing an expedition back into the jungle to locate the vein from which more such stones can be mined. Hamegg is only interested in the whole adventure for what glory he can wring out of it, and he sees the jungle as one giant predator to be tamed.
Mustache is more compassionate and compulsively locks horns with Hamegg. The two soon part ways, with Hamegg slashing and burning his way through the landscape and Mustache attempting to co-exist as best he can. When a plague begins spreading through the jungle, Mustache realizes his antibiotics may be of use, and soon finds a way to parlay that into getting help from the animals — even though he doesn't quite understand how to go about it at first. (Longtime Tezuka fans will realize Hamegg and Mustache are part of his extended gallery of continuing characters who turn up in many different works by him; they're impossible to miss in Metropolis as well.)
Lune's curiosity about the human race eventually leads him
to the circus and into the arms of Mary, the trapeze artist.
There is, incredibly, yet another plot that splits off from these two, one which involves Lune being swept out of the jungle by a flood and into the arms of a couple of unscrupulous fishermen. They sell him off to the circus for a handsome price, and it's there that Lune learns about the divisive realities of human nature up close. He sees the circus creatures being brutally mistreated, but he also becomes good friends with the trapeze girl, Mary. She's wise enough to understand that Lune's home is not with her, but with her own kind in the jungle — especially when she sees Lune directing other animals to help put out a massive fire in the campgrounds.
The problem with the story is not the drama per se but the storytelling. Too much of each branch of the plot is delivered all at once, in big chunks, without enough intercutting or leavening to raise the tension and give things a little more textural variety. The end result feels weirdly callous: we follow sets of characters for so long that it feels like the movie has simply forgotten about the rest of the cast. In the end that's unfortunately what it's tantamount to — too much of one important side of the story (Lune's journey home) is simply not told, and it feels sloppy. Worse than sloppy, in fact: it feels downright inconsiderate.
Still, it would be unfair to call this a bad movie. So much of the film is, indeed, so good that it almost makes the stilted storytelling irrelevant. There's one moment near the end, involving a moral choice on the part of one of the characters, that is astonishing — it's so forceful that it comes close to redeeming the rest of the movie single-handedly. And there are many grand moments of pure action, as when a pack of coyotes attack the Earth Mother in a snowstorm. The animation isn't quite as polished or assured as Metropolis or Miyazaki's work (which is, I find, fast becoming the gold standard against which movies like this will be compared), but it's fluid and competent.
The real heart of the story lies with, as with all Tezuka's work, the way characters grapple with massive moral choices. I just wish the film had been more elegant in delivering that material. It's one thing to have a movie contain a message, and another to have it bring it to its audience with the sophistication and grace needed to really make it hit home. What we have here is not a bad movie, but something a little more problematic: an okay movie that suffers by not being a great one.