Kaiki Daisakusen (怪奇大作戦 Kaiki Daisakusen?) is a mystery supernatural show produced by Tsuburaya in 1969. It was filmed after the production of Fight! Mighty Jack. Tsuburaya Productions' official international title for the series is Operation: Mystery.
Rather than focus on giant monsters, Kaiki Daisakusen focused on more paranormal phenomenon, revolving around the exploits of the Science Research Institute team (SRI) as they combat these threats.
To date, there have been three sequels/remakes of Kaiki Daisakusen.
- Science Investigation SRI: The Laughing Man In Flames [ 怪奇事件特捜チームS・R・I 嗤う火だるま男 Kagaku Tokusou SRI: Warau Hidaruma Otoko] - 2004
- Operation: Mystery - Second File [怪奇大作戦 セカンドファイル Kaiki Daisakusen: Second File] - 2007
- Operation: Mystery - Mystery File [怪奇大作戦 ミステリー・ファイル Kaiki Daisakusen: Mystery File] - 2013
In 2012, Tsuburaya Productions released a DVD of Operation: Mystery in HD.