Three tales based on the Gradius video game series by Konami. The planet Latis is under attack by the Space Dragon Salamander and it's war planet, the Bacterian horde destroying everything in sight, their defenses ineffective and losing all hope, three heroes from the planet Gradius join Lord British in defense of his beloved planet. 
Then in a prequel, a girl from a distant planet brings an ominous warning to the planet Gradius, the Bacterians and how three people become heroes of the galaxy. 
Then we jump to the future, after the signing of a peace treaty, one of our heroes gets captured by the Bacterians, can the military might of Gradius and our remaining heroes save the prisoner from a fate worse than death. 
(Source: AniDB)