Prostu★dent Good

The year is 2005 in Japan. The world has received word that aliens shall invade Earth. Therefore, Japan set up a robot group called Yugoku to fend off the aliens when they come. However, the aliens never came, so Yugoku was all for nothing. Meanwhile, the Japanese government was totally corrupted, and Yugoku decided to use their robot army to overthrow the government.

[Edited from Anime Densetsu]