Omoikkiri Tanteidan Haado Gumi: Matenrou no Chousenjou

A group of five detective kids are on a mission to retrieve various objects stolen by a mysterious thief who wears a golden mask. The group counts the leader Hiroshi, the cute and Aikido expert Yasuko who also happen to be the only girl of the group, Susumu, Satoru and Takeo. The mysterious thief uses many ingenious tricks to escape his pursuers, such as a huge and colorful air-balloon.