Ultraman: S1 E18 - Brother From Another Planet
Radiation fog suddenly occurred at night in Tokyo, and what appeared from there was Alien Zarab, which calls itself as "Bother of eathlings". It shows friendly attetude to earthlings, but its true purpose was to invade Earth. Hayata noticed its plot but was captured by Alien Zarab. Immediately after that, Ultraman appeared and began to destroy the city!