Celebi, the Mythical Pokémon revered as the "Voice of the Forest," drives the narrative of its film through extraordinary time-travel abilities, drawing relentless pursuit from those coveting its powers. Forty years prior to the main events, a Pokémon Hunter wounds Celebi during a forest chase. A young boy named Sammy shields the injured Pokémon, prompting Celebi to activate its powers in desperation. This action inadvertently transports both Celebi and Sammy to the future, stranding Sammy far from his era. In the present, Celebi resurfaces alongside Sammy in the same forest but flees, weakened and wary. Ash and his companions encounter Sammy and locate the elusive Celebi, gradually soothing its fears with care. Guided by wild Pokémon, the group journeys to the Lake of Life—a sanctuary with purifying waters—where Celebi heals fully, revealing a playful and affectionate nature toward Ash and Sammy. Celebi’s fragility is weaponized when the Iron Masked Marauder, a Team Rocket operative, ensnares it using a corruptive Dark Ball. This device twists Celebi into a malevolent force, maximizing its power to construct a rampaging armor of vines and trees that devastates the forest. During the chaos, Ash and Sammy breach the armor, reaching Celebi. Their emotional plea shatters the Dark Ball’s control, restoring Celebi’s true essence—but the trauma leaves it fatally drained. A convergence of Celebi from across time resurrects the fallen guardian at the Lake of Life, demonstrating their timeless unity. Celebi then returns Sammy to his original era, affirming its role as a keeper of temporal harmony. In a post-credits revelation, Sammy matures into Professor Oak, preserving his encounter through sketches of Celebi and Pikachu.