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.

"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)

As a baby Jiro was delivered to his foster parents by a massive oni, who said he would return for Jiro in 15 years. When the time comes Jiro must contend with enemy oni, dark cultists, and their minions while attempting to protect both his parents and girlfriend from their depredations. Ultimately he must embark on a journey through the past, future, and other dimensions to embrace his destiny as Shuten Doji reborn.

Looking at Miyuki and Tatsuya now, it might be hard to imagine them as anything other than loving siblings. But it wasn't always this way.. Three years ago, Miyuki was always uncomfortable around her older brother. The rest of their family treated him no better than a lowly servant, even though he was the perfect Guardian, watching over Miyuki while she lived a normal middle school life. But what really bothered her was that he never showed any emotions or thoughts of his own. However, when danger comes calling during a fateful trip to Okinawa, their relationship as brother and sister will change forever…