Ultraman Season 2

Summary:

Note: Based on a manga sequel of the 1966 Ultraman tokusatsu television series written by Shimizu Eiichi and drawn by Shimoguchi Tomohiro.

A global mass disappearing event takes place among humanity. Rena and Shinjirou simultaneously vanish. In the wake of these events, freelance journalist Higashi Koutarou investigates this mysterious "disappearance incident." The aliens behind it are the terrorist organisation Dark Star. They transmit a message to those on Earth.
"Give us half of the Earth, or sacrifice half of its people... make your choice".
At the same time, the recently disappeared Rena and Shinjirou are teleported to the Dark Star ship orbiting the Earth.

Learning too much, Koutarou is caught in the crossfire between Dark Star and the SSSP, and is almost left for dead.... In the final battle, our heroes face off against the Golden Fortress. Facing this giant mecha destorying the city, ULTRAMAN, SEVEN and ACE are joined by ZOFFY, JACK, and TARO. At long last the 6 ULTRAMAN heroes have assembled!

AniDB