Keisuke Jin (神 敬介, Jin Keisuke) is the main protagonist of Kamen Rider X. He was remodeled by his father, Keitaro Jin, into a Kaizorg (カイゾーグ, Kaizōgu), a cyborg built for undersea exploration, becoming X-Rider (Xライダー, Ekkusu Raidā). He is also otherwise referred to by the title Kamen Rider X (仮面ライダーＸエックス, Kamen Raidā Ekkusu, Masked Rider X).