One Punch Man: Road to Hero Episode 1: Episode 1
OVA bundled with the 10th volume of the One Punch Man manga. It features an original story by the series' mangaka, ONE, about the secret story of the birth of Saitama's hero suit.
Where to watch
Not currently listed with a streaming service.
JustWatch comparison: streaming options for One Punch Man: Road to Hero
Episode listings and service links are from the AniList open database. Watchanimee does not host, mirror or proxy commercial anime streams.