Michael B. Jordan worked many excellent anime references into his directorial debut Creed III, but one classic anime that inspired the film is worth seeking out, the boxing shonen series Hajime No Ippo. The long-running manga has been releasing new chapters since 1989. This led the same animation studio that released Death Note and Hunter X Hunter, Madhouse, to release a 76-episode series titled Hajime No Ippo: The Fighting! between 2000 and 2002 that holds up incredibly well.
https://screenrant.com/creed-iii-anime-inspiration-hajime-no-ippo-must-watch/