A hidden, recessive program deep within the SPT-LZ-00X Layzner capable of overriding Rei, this AI had the persona of an adult male yet still kept the amorality of its predecessor. Programmed by Ken Asuka as a way of conveying information about Grados to the Earthlings, Fouron would only ever surface when the Layzner was critically damaged or Eiji was in serious danger of dying: its trademark purple eyes marking its complete control over the SPT, even its V-MAX system.

The SPT Lazner is a super-powered, computerized Tracer robot. It is the strongest robot in the universe. The story's hero, Eiji, is the child of an earthman and an alien from another planet. He happens to find out about a conspiracy to destroy the earth. Using Lazner and with his friends’ help, Eiji decides to save his father's planet earth and fight against his mother's planet to achieve peace in space. 
 
The Story takes place in an alternate reality based in the year 1996, where humanity is advanced enough to develop long-range space travel. 
 
(SOURCE: AnimeNewsNetwork)

The Layzner OVA serves as an alternative version of the TV series. 
The first episode, titled "Eiji 1996", recaps the first part of the series (episodes 01-24). 
The second episode ("Le Caine 1999") takes place after a time skip, and contains episodes 26 through 37 (episode 25 of the TV series, being a recap itself, is skipped here). 
The final episode, "Seal 2000", is an expanded version of the final episode of the TV series (38) and features new animation and a longer epilogue.