Ultraseven: S1 E41 - Challenge From Underwater Ultraseven

Members of the Japan Kappa Club headed towards Lake Ishu, where the legendary creature Kappa was rumored to be found. At the same time, Ultra Guard was also heading towards Lake Ishu to investigate an UFO. Takemura, a member of the Japan Kappa Club was killed. The truth turned out to be a race of aliens who had the same appearance of Kappa were lurking in the lake waiting for Earth invation!