One Piece: Season 21, Episode 1013

21 - 1013: Yamato’s Past! The Man Who Came for an Emperor of the Sea!

Yamato tells Momonosuke and Shinobu that he once confronted a man, who came to Onigashima looking to get Kaido’s head. His name was Ace. The two of them engaged in a fierce battle that eventually turned into an important friendship.