Netflix's One Piece: How Does Kuina Die?
In Episode 4 of Netflix's live-action "One Piece" adaptation viewers learn Roronoa Zoro (Mackenyu)'s backstory, which revolves around the death of a girl named Kuina (Audrey Cymone).
In a multi-part flashback sequence, a young Zoro (Maximilian Lee Piazza) loses two duels against Kuina before they vow to train together until one of them becomes the greatest swordsman in the world. One day, however, Zoro shows up to their meeting spot where his sword-fighting teacher Shimotsuki Koushiro (Nathan Castle) greets him in Kuina's stead. Koushiro lets Zoro know that Kuina died in an unspecified accident.
Since he provides no further details about her death, viewers are left hanging about just what happened to Kuina. As it turns out, the "One Piece" manga on which Netflix's show is based does, in fact, specify what killed her — the day after she and Zoro decide to train together, she dies after falling down a staircase. It's entirely possible that the Netflix adaptation omits this detail because, as a cause of death, falling down a staircase could comes off a little goofy during what's otherwise a serious character moment. But unless the show at some point states otherwise, it's safe to assume her cause of death remains the same, even if it's never explicitly clarified.
The motivation Kuina provides Zoro remains consistent
Of course, the nature of Kuina's death is ultimately unimportant in light of the motivation it provides Zoro. When Luffy (Iñaki Godoy) first meets him in Episode 1, Zoro makes it clear that his ultimate goal in life is to become the greatest swordsman in the world. It's the fact that he vowed to be one of two people to accomplish this ambitious task only to lose that other person, viewers find out in Episode 4's flashback sequence, that drives him to do so.
Perhaps complicating matters is a conspiracy among some "One Piece" fans that Kuina is still alive. One detailed theory full of late manga spoilers circulated by Reddit user dodomangus proposes that the Marine swordsman Tashigi is actually Kuina. Zoro remarks that Tashigi resembles his childhood friend as soon as he meets her, but the manga has yet to ascribe any significance to this resemblance.
If this theory is true, then the Netflix "One Piece" series may have omitted Kuina's cause of death to make room for the reveal of her survival. Since this is currently within the realm of conspiracy, however, viewers can assume for the time being that the live-action version of Kuina also died after falling down a flight of stairs.