The episode features flashbacks revealing the sacrifice made by Ace's mother, Portgas D. Rouge , to save him. It also covers the secret of his connection to Luffy and concludes with Whitebeard making a dramatic entrance at Marineford. Arc: Marineford Arc (Season 14, Episode 2).
"Paper" for likely refers to the Episode 460 summary or manga chapters that it adapts. One Piece Episode 460
Shown in a flashback during the reveal of Ace's true lineage. The episode features flashbacks revealing the sacrifice made