Daiki Kaito is a major character in the 'Kamen Rider Decade' series, appearing as Kamen Rider Diend. He is a mysterious treasure hunter who travels across different worlds to steal valuable artifacts, often clashing and cooperating with the protagonist, Tsukasa Kadoya (Kamen Rider Decade). Known for his cunning and playful demeanor, Daiki operates with his own set of morals and adds complexity to the story by serving as both a rival and an occasional ally. His unique blue Rider suit and Diendriver weapon distinguish him from other Riders.