Tsukasa Kadoya (門矢 士, Kadoya Tsukasa) is the main protagonist of Kamen Rider Decade. He is an interdimensional traveler who transforms into Kamen Rider Decade (仮面ライダーディケイド, Kamen Raidā Dikeido) to oversee the fate of the multiverse, embracing his role as the Destroyer of Worlds (世界の破壊者, Sekai no Hakaisha). Tsukasa later returns in Kamen Rider Zi-O as a major supporting character as he observes the actions of Sougo Tokiwa and their effects on the timeline.