A lion cub finds a music box in plane wreckage and becomes obsessed with the humans who made it, while his father Leo tries to protect a jungle that doesn't want protection from anyone. The movie moves at the pace of a fable, more interested in what curiosity costs than in spectacle. Tezuka builds something genuinely strange here: a story about inheritance and refusal, where the real conflict isn't between hero and villain but between a father trying to pass down a world and a son who wants to understand the creatures destroying it first.
Leo's reign over the jungle faces its greatest test when his son Lune discovers a mysterious music box among airplane wreckage, igniting a dangerous fascination with the human world. Meanwhile, the ruthless treasure hunter Ham Egg arrives with armed mercenaries, tearing through the forest in search of the Moonlight Stones, mythical gems rumored to solve humanity's energy crisis. Standing against this destruction are two unlikely allies: the eccentric Dr. Moustache and his companion Lemonade, determined to protect the jungle from exploitation. When a devastating plague sweeps across the animal kingdom, the lines between human and beast blur as salvation comes from an unexpected source. Yet salvation comes with a cost. The path to genuine salvation lies hidden atop the legendary Mt. Moon, where answers about the stones, the virus, and the future of both worlds await. Lune must reconcile his curiosity about humanity with his duty to his pride, all while environmental destruction and natural disaster threaten to reshape everything he knows.