"Pokémon 3D Adventure: Mew o Sagase!" is a short anime special that blends traditional 2D animation with 3D CGI elements, creating a unique visual experience. The story centers on a young boy named Toshiro, who is transported into the Pokémon world through a mysterious virtual reality device. Upon entering this digital realm, Toshiro encounters Pikachu, who becomes his companion as they embark on a quest to find the elusive Mythical Pokémon, Mew.

The narrative unfolds as Toshiro and Pikachu navigate a series of challenges and puzzles within the virtual world. They encounter various Pokémon, including a mischievous Gengar and a helpful Bulbasaur, who aid them in their journey. The duo must overcome obstacles such as a maze-like forest, a treacherous mountain, and a cavern filled with traps. Along the way, Toshiro learns about teamwork, courage, and the importance of perseverance.

The climax of the story occurs when Toshiro and Pikachu finally locate Mew, who tests their resolve by creating illusions and challenging their determination. Through their unwavering spirit and cooperation, they prove themselves worthy, and Mew reveals itself, rewarding their efforts with a glimpse of its playful and enigmatic nature. The special concludes with Toshiro returning to the real world, carrying with him the lessons and memories of his extraordinary adventure.

The main characters include Toshiro, a curious and determined boy; Pikachu, his loyal and resourceful Pokémon companion; and Mew, the mysterious and powerful Mythical Pokémon that serves as the central focus of their quest. The story emphasizes themes of exploration, friendship, and the bond between humans and Pokémon, all while showcasing a blend of traditional and modern animation techniques.