The first episode, Aoi Hitomi no Casval, tells the story of Casval Rem Deikun and Artesia Som Deikun (Char and Sayla, before Char became known as the Red Comet) before the One-Year War in UC.0068.
The story for the second episode, Kanashimi no Artesia, moves three years ahead to U.C. 0071. The story will follow the tearful separation of the siblings Casval and Artesia (before they became known as Char and Sayla). It will also feature more of the development of the mobile suits, particularly on the Zeon side.
The third episode, Akatsuki no Houki, follows the youth who would become known as Char Aznable and his future comrade Garma Zabi after they join the Zeons' military academy.
(Source: Anime News Network)
— Description from AniList community (anilist.co).
