Ziin (ジーン, Jīn) is an audience member of the Desire Grand Prix and Ace Ukiyo's supporter who transforms into Kamen Rider Ziin (仮面ライダージーン, Kamen Raidā Jīn). During the third Desire Royale, he transforms into Kamen Rider Ziingazer (仮面ライダージーンゲイザー, Kamen Raidā Jīngeizā).