クロトーが京都で新たなケミー、UFOエックスを捕獲。 冥黒の三姉妹が企む謎のドライバーと関係があるようで・・・ 一方、引き続きケミー回収に勤しむ宝太郎たち。 彼らが次なる回収に狙うのも、UFOエックス！ 実は、UFOエックスは錆丸が長年憧れていた存在。 期待とガッチャに胸を膨らませる宝太郎。 そこに、錬金連合から派遣された2人の調査官、 釘宮と針磨がやってくる。 釘宮から「仮面ライダーとして認めない」と宣言される宝太郎。 ドライバーを渡すよう迫られるが・・・ そんな中、富良洲高校に冥黒の三姉妹が出現！ 三姉妹の目的とは？ そして、宝太郎は仮面ライダーとして力を見せることはできるのか？
Kuroto captures a new Chemie, UFO X, in Kyoto. It seems that it has something to do with the mysterious driver that the Three Dark Sisters are plotting... Meanwhile, Houtarou and his friends continue to work hard to recover Chemie. Their next target for recovery is UFO X! In fact, UFO X is something that Sabimaru has admired for many years. Houtarou's heart swells with anticipation and excitement. Two investigators dispatched from the Alchemy Federation, Kugimiya and Harima, arrive there. Houtarou is declared by Kugimiya that he will not be recognized as a Kamen Rider. They are forced to hand over the driver, but... Meanwhile, three dark sisters appear at Furasu High School! What is the purpose of the three sisters? And will Houtarou be able to show his strength as a Kamen Rider?
