Uo Uo no Mi, Model: Seiryu

Counted within the strongest tier of Devil Fruits, this Mythical Zoan grants transformation into a hybrid or a full Azure Dragon, the Eastern serpent-dragon of Chinese myth. Despite picturing a dragon, its name leans on uo, Japanese for fish, a nod to the East Asian lore in which carp ascending a waterfall become dragons. The fruit was once a treasure of the World Nobles before Charlotte Linlin seized it and Kaidou devoured it during the God Valley Incident some thirty-eight years ago.

Years later, the scientist Vegapunk drew a sample from a captured Kaidou's Lineage Factor and manufactured an artificial duplicate. Because the resulting dragon came out the wrong color, he judged the project a failure, which inadvertently led the World Government to dismiss the fruit as useless. That replica was eventually eaten by Kouzuki Momonosuke, giving him a dragon shape nearly identical to Kaidou's apart from its pink hue.

As a Mythical Zoan, the fruit dramatically amplifies the user's raw power, far beyond ordinary Zoan types. In his full beast state Kaidou swells to roughly the size of a small town, ranking among the largest transformations ever shown, and a single swipe of his comparatively slim arms can hurl fish-men through rock or tear houses apart. His scales are famously durable, shrugging off conventional Armament Haki entirely, though attacks that bypass external defenses, advanced emitted Armament Haki, powerful soundwaves, surgical techniques, or Supreme King Haki infusions, can still draw blood. Smaller foes are matched in speed despite his bulk.

Beyond the body itself, the fruit bestows more supernatural gifts than any other Mythical Zoan seen so far. Chief among them are the Flame Clouds, fiery footholds the user conjures to fly and even to hoist entire islands aloft, no transformation required to maintain them. The wielder also commands the elements, breathing concentrated fire, loosing lightning with a roar, slicing the air with wind blades, and stirring up tornadoes. The Human-Beast Form trades colossal size for agility and close-combat prowess while keeping the elemental arsenal at reduced range.

The drawbacks track with the user's enormity: the full dragon struggles in tight quarters, courts collateral damage, and presents a broad target for multi-directional assault. Flame Clouds weaken as the user nears physical exhaustion, can be doused with water, and vanish entirely should the user lose consciousness. Fire breath, too, can be cut by those skilled in the Foxfire Style.

Kaidou is the natural wielder and leans on the power constantly in battle. He often opens fights as a full dragon, hovering at range to bombard enemies with elemental attacks, then reverts to human form for serious close combat, escalating to his Human-Beast Form, arguably his strongest stance, against opponents who can handle the other two. His signature techniques include Bolo Breath, a sweeping conical blast of fire, Kaifu, crescent wind blades, Tatsumaki, a coiling tornado, and Kaen Daiko, a fire dragon that engulfs his own body. When drunk enough to acknowledge a foe, he engages in Shuron Hakke, switching forms unpredictably and even manifesting unique shapes.

Kouzuki Momonosuke holds the artificial copy. After being aged to adulthood by Shinobu's Juku Juku no Mi, he came to wield strength, fire breath, and Flame Clouds much like Kaidou, including his own Bolo Breath that he turned against Aramaki, though he is still mastering the gift. Notably, according to Oda, Roronoa Zoro would carry this fruit if granted one, absorbed into one of his swords.