This is a documentary-style animated special drama that tells the story of Shigeo Nagashima, a representative postwar baseball player who was also known as "Mr. Giants" when he was still playing for the Yomiuri Giants. The story is just after the end of the war.
Watch Mister Giants Eikou no Sebangou 3 episode 1 online — subbed and dubbed, with automatic AniList / MyAnimeList progress sync.