Completing every job with ruthless accuracy, Train Heartnet is an infamous assassin with no regard for human life. Donning the moniker "Black Cat" in the underground world, the elite killer works for the powerful secret organization known only as Chronos. One gloomy night, the blasé gunman stumbles upon Saya Minatsuki, an enigmatic bounty hunter, and soon develops an odd friendship with her. Influenced by Saya's positive outlook on life, Train begins to rethink his life. Deciding to abandon his role as the Black Cat, he instead opts to head down a virtuous path as an honest bounty hunter. However, Chronos—and particularly Creed Diskenth, Train's possessive underling—is not impressed with Train's sudden change of heart and vows to resort to extreme measures in order to bring back the emissary of bad luck. This assassin turned "stray cat" can only wander so far before the deafening sound of gunfire rings out. [Written by MAL Rewrite]

Zoids are beast-like fighting machines used in both everyday use such as transportation, and special use such as war. Some types of Zoids, know as Organoids, are miniature Zoids that are living organisms. These Organoids have the capability to fuse with a non-living Zoid and make it much more powerful. Van (Ban) Freiheit discovers a Zoid Organoid in an abandoned laboratory while running from two strangers piloting Zoids. Also in the laboratory, in an animated suspension tube is a strange girl. He breaks the tube open and takes her and the Organoid with him. Spotting a ruined Shield Liger Zoid outside nearby, the Organoid fuses with it and repairs the damages. Making his escape, Van names the Organoid Zeke, and decides to keep him as a friend. The girl, who says her name is Fiona, wants to find something called Zoids Eve, and so Van, Zeke, and Fiona begin their adventure. (Source: AniDB)

This story follows a boy named Quon and his friends, who are "Attractors." Attractors are human beings who have awakened and have supernatural powers. Quon is determined to save them all. But a secret organization is hunting them...

The year is 2148. Two years after the end of the original Fafner in the Azure TV series, Tatsumiya Island and its surviving residents have returned to some semblance of recovery. However, things have become desperate for our hero, Kazuki; nearly blind now, and partially crippled from his battles with the Festum two years earlier, he clings to the promise his fallen friend Soushi made to him to return to the island and set things right again. Kazuki's hopes flare when a lifeform is detected within an unmanned submarine that comes floating into Tatsumiya Bay one night, but the person aboard isn't Soushi; it is a mysterious "boy" named Misao Kurusu who may not be entirely human, and who claims to have been sent by Sōshi. With Misao's arrival, hostilities break out anew between the Human Army and the Festum, and the Fafner pilots are thrown into the most desperate battle of their lives - this time, with the fate of TWO races riding on their shoulders. 

(Source: Wikipedia)