「我が名は鳳桜・カグヤ・クォーツ。貴様にはゴージャスが足りない」
宝太郎は、並行世界に突如転移し、謎の男、鳳桜・カグヤ・クォーツと出会います。この世界の技術"オーロラカーテンシステム"を使って宝太郎を呼び寄せた彼の目的とは…？
鳳桜・カグヤ・クォーツは自らのことを「カグヤ様」と自称し、ゴージャスな衣装を身に纏い、自らの名を冠した「鳳桜タワー」の最上階に暮らすゴージャスな男。
加治木にそっくりな執事のバトラーを従え、悪の組織「ハンドレッド」の魔の手から世界を守る仮面ライダーレジェンドへと変身します。
Houtarou is suddenly transported to a parallel world. Awaiting him is a young man named Houou Kaguya Quartz who summoned him using that world's technology, the Aurora Curtain System. His favorite phrase is "Gorgeous" and he protects the world from the clutches of the evil organization called "Hundred". What's more, the person following Kaguya is a butler named Butler, who looks exactly like Houtarou's friend Ryo Kajiki!
Kaguya gathers the power of past Kamen Riders who exist in parallel worlds in order to fight against the Hundred. However, unlike the other Kamen Riders, he seems unable to gain power from Gotchard, who is "not gorgeous". Kaguya brought Houtarou into his world in order to make him gorgeous.
