The Hira Hira no Mi is a Paramecia-type Devil Fruit that allows the user to make their body and any object they touch become flat and flexible, letting solid objects ripple, billow, and flutter like a piece of cloth or a flag. The user is described as a Flag Human (旗人間,Furaggu Ningen?) due to the visual effect of these powers. It was eaten by Diamante.
This fruit allows the user to make their body and anything they touch gain the malleable properties of cloth fabric. As such, the affected materials become completely flexible, flat, and foldable, and weigh a fraction of their usual mass; this effect is strong enough to let hardened metal flutter like a flag in the breeze at the user's command. At the same time, all other natural characteristics such as toughness, strength, or sharpness are retained by the material, so metal objects can still resist forceful impact from enemies and blades retain an edge. The user can creatively fold and reshape flattened items into different forms and shapes. It is unknown if the power can be used on other living things, besides the user themselves.
This fruit does not seem to have any specific weaknesses, aside from the standard Devil Fruit weaknesses.
Defensively, Diamante has been seen using a cape made from a steel block as a shield, allowing it to flutter unsuspectingly until he is attacked. This allows him to break oncoming swords on impact. By applying this ability onto himself, he can flatten his entire body into a flag-like state, allowing him to float safely when falling.
Offensively, he can apply this ability onto his rapier, lengthening the blade and transforming it into an urumi, which in turn allows him to reshape it into a mace or to assault at various unsuspecting angles. He can also hide other weapons on his body, such as a mace by flattening it into a medal, and folding it up.
Lock (ロック,Rokku?): Diamante undoes his power on something that he has used his powers on to return that object to its original state of matter. Diamante first used this technique to change the shape of his sword. It presents an imposition of some kind of hardening effect when using this ability, significantly increasing its standard durability. An example of this was when the pirates tried to attack the SMILE factory and Diamante used his power on a wooden pole and made it much denser than normal, using it as a weapon.
Corrida Glaive (闘牛グレイブ,Korīda Gureibu?, literally meaning "Bullfighting Glaive"): Diamante uses his sword and flattens it to reform and fold it in the form of a bull's head, effectively forming a stylized mace, which he uses to strike his opponent. This was first used against a group of gladiators who tried to argue against Rebecca's victory.Corrida translates to "race" in Spanish and Portuguese.
Vipera Glaive (蛇の剣,Wīpera Gureibu?, literally meaning "Snake Sword"): Diamante flattens the blade of his sword. The flattened blade will then extend itself and move like a snake towards a target in order to cut them. This was first used against Rebecca, but was intercepted by Kyros.Vipera is a genus of venomous vipers.
Army Bandera (陸軍旗,Āmī Bantera?, literally meaning "Army Flag"): Diamante makes the ground he is standing on ripple and flutter, making it difficult for all nearby foes to move and stand on it. This was first used on Flower Field, causing Kyros to lose his footing.Bandera is the Spanish, Catalan, and Filipino word for "flag".
Hira Release (解除,Hira Rirīsu?, literally meaning "Release"): Diamante releases the effects of his Devil Fruit on an object, causing it to return to its original shape. This was first shown in the Colosseum when unfolding a mace against Rebecca, but was named in the fight against Kyros.
Death Enjambre (死の星屑,Desu Enhanbure?, literally meaning "Stardust of Death"): Diamante pulls out several folded up confetti cannons, undoes his powers over them, and fires them all at once. He then uses Hira Release on the "confetti" high in the sky, revealing it to be spiked iron balls that he had flattened with his powers. The iron balls then fall to the ground like rain, a sight Diamante compares to "falling stardust". According to Diamante, this technique's destructive power is enough to wipe out an entire army. To defend himself from the raining steel balls, Diamante unfolds a steel umbrella in his own possession. This was first seen used against Kyros, Rebecca, and Robin.Enjambre is the Spanish word for "swarm".