Manami is your typical schoolgirl, despite the odd machines her grandfather is always building. One day, though, an odd evil robot comes to attack Minami's school, and commits the ultimate offense of threatening her friends... and ruining her lunch. Now, she will stop at nothing to return order to the world in her grandpa's newest creation: the mecha Del Power X.

Unidentified creatures "Archon" suddenly appear and bring the human beings to a crisis of extinction. A special corps "Goulart Knights" is formed to counter attack Archon. The knights have supernatural power to generate "Holy Grail" from their spirits and battle against Archon.

While looking for the ledgendary Mapman, the last surviving member of the Nomad Star tribe, Lipumira finds him in Tokyo. His name is Gen Tokishima and he is the only one able to get one part of the starmap hidden within the Earth. After retrieving the piece, Gen must make a decision to follow Lipumira in her foolhardy search to find the remaining pieces of the starmap or stay on Earth. He makes his decision, only to find his girlfriend has beaten him to the spaceship as she wants to come as well. Unfortunately, as Gen learns the secret of the starmap, Lipumira's sisters have plans to stop her and will stop her at any cost.

"How were Gaia Memories created?" "Why did W begin to fight?" To answer Tokime's questions, Shoutarou quietly begins to tell a story. He speaks of his meeting and parting with a man he admired and called his old man—his mentor, Soukichi Narumi. Mysterious people called Dopants, who utilized the powers of Gaia Memories, had begun appearing in the shadows of Fuuto, the windy city. A young Shoutarou had become an assistant of the detective Soukichi and, though called half-baked, began to follow in his footsteps. Unaware that, in addition to his detective work, Soukichi was secretly acting as Skull, Shoutarou began to grow frustrated with his mentor. That was when the Narumi Detective Agency received a phone call—a request from Hell inviting Shoutarou and company to a fateful night! When Shoutarou tracked down Soukichi to deliver the "trump card" bestowed by the mysterious caller, what did he see? Shoutarou and Philip. The one detective made of two and the night when Kamen Rider W began. That whole story will finally be revealed. (Source: Official site, translated)