Search 1: "The Kamen Rider Case"

Search 1: The Kamen Rider Case (サッチ1：仮面ライダーの事例) is the first episode of Kamen Rider Tantei. It features the debut of Kamen Rider Tantei's base form, and a glimpse of Tantei's Spy Form and Jane Doe.

Snynopsis
Dective Hiroshi Yanami seems like an ordinary person, but something is just... abnormal. One day, he finds a strange belt and a fedora on the ground, but what he doesn't know is that it'll transform him into the case-solving hero, Kamen Rider Tantei!