The staring of this story is Tsukasa Kadoya, a boy who adventuring to Kamen Rider Heinsei from Kuuga until Kiva. Storied that each that world closing to blowing because thats will be meet, and Tsukasa must be prevent that. While, Tsukasa lost his memories and in his mind, he only looking for where he came from. 
A girl named Natsumi Hikari often dream about the fight of Kamen Rider Heinsei. In her dream, Kamen Rider united to face an enemy, but the enemy is so strong and one by one Kamen Rider going down. A shadow showing to Natsumi and say a word ; "Decade...". Then Natsumi meet Tsukasa, then something happen in that day she meet him. The city close to destruction, and the monsters show make civilian panics. In that moment, Tsukasa see Wataru Kurenai who know that Tsukasa is the Kamen Rider Decade. He fight with Worm the monster in Kamen Rider Kabuto but he don't really know what he do because of the lost of his memories. Wataru says that he must going to 9 Kamen Rider's worlds to save the world. Natsumi want to follow Tsukasa to his journey because she want to know the meaning of her dream. But in every Kamen Rider's world, Decade seeing as the enemy. Can he find the truth about himself...?
