Spoiler Warning: The following contains major spoilers for One Piece
Everyone knows that flashbacks are never the best part of a story. At best, they give crucial information that sets up and explains the actual story and characters. At worst, they come off as wasting time. Either way, flashbacks aren’t known for being good stories by themselves. None of this applies to One Piece. In One Piece, flashbacks frequently accomplish their usual goals, but also provide some of the best parts of the entire anime. One Piece has had a lot of flashbacks, but for this article I’ll be focusing on Robin’s backstory, which is by far the most memorable and contains all of what makes One Piece flashbacks so great.
Robin’s flashbacks reveal how her home island, Ohara, was destroyed by the World Government because the scholars there were conducting forbidden research into the world’s history. Robin survived with the help of Jaguar D. Saul, a Marine who refused to participate in the destruction of Ohara. Saul was killed while helping her, but the Marine who killed him chose to spare Robin’s life. Robin was the only survivor and was hunted by the government ever since.

Robin escaping Ohara.
In terms of the main story, her flashback serves to explain her actions and why she left the Straw Hats when the government came after her. That alone would work in most stories, but One Piece handles it somewhat differently. Instead of treating it as something supplementary to the main story, her backstory is treated as a story in and of itself. The show takes time to establish her situation on Ohara, her relationship with the scholars there and her growing friendship with Saul. Even though things are obviously going to end badly, you can’t help but get invested in the characters there. Saul’s death and Robin fleeing the island feel as much like the conclusion of a story arc as the end of a series of flashbacks. The final scene of Robin crying in the boat while trying to laugh it off like Saul taught her is genuinely heartbreaking precisely because the story makes you care about her, Saul and the people of Ohara.
Part of what makes this backstory (and most One Piece backstories) so effective is how strongly it contrasts with the main series. One Piece is at its core an optimistic show. It has darker arcs, but is generally fun and upbeat. The backstories are decidedly not upbeat. Understanding Robin’s past makes you even more invested in the main story. You really want to see her find happiness after everything she went through there, and when the story provides it’s resolution, it’s immensely satisfying. Robin shouting that she wants to live wouldn’t have been nearly as satisfying if her backstory had just been exposition instead of working to tell a story all on its own.
While I’ve only talked about one specific backstory, the things that made it so good apply to most One Piece backstories. To put it simply: the flashbacks told a story instead of giving information to supplement another story. This distinction is what makes One Piece flashbacks so good compared to what people normally expect from flashbacks.
One Piece is available from Funimation and is available for streaming on their website, as well as on Crunchyroll.