LEGEND OF THE GALACTIC HEROES: MY CONQUEST IS THE SEA OF STARS

This movie, based on an anecdote of "Ginga Eiyuu Densetsu" written by novelist Tanaka Yoshiki, preludes the 110-episodes TV series by describing the first encounter between the ambitious young man Reinhard von Museal under the imperial flag and the passive Yang Wenli who serves a corrupting democracy. Set in an imaginative future, the story describes the first encounter between Yang and Reinhard and discusses how heroes are born. (Source: Anime News Network) — Description from AniList community (anilist.co).