How exactly does eating a Devil Fruit work? Where does the ability live inside the body? And how does Blackbeard steal powers from the dead? This article breaks down the mechanics of Devil Fruit transmission — and why Vegapunk called Momonosuke’s artificial fruit a “failure.”
The Conditions for Devil Fruit Transmission
How Much Do You Have to Eat?
Law and Buggy swallowed their fruits whole. Luffy and Sabo each took one bite. Kaku peeled his like a banana and ate just the fruit itself — no skin required. Kalifa cut hers with a knife and fork and ate only one small piece.
What this tells us: you only need to eat the fruit itself (not the skin), and a single bite is enough.
But what about objects that ate Devil Fruits? What does it even mean for a gun or a sword to “eat” something?
Guns Have a “Mouth”
Breaking down the act of eating: (1) putting something in your mouth, (2) chewing, (3) swallowing.
From Buggy and Law, we know chewing isn’t required. From Kaku and Kalifa, we know that the devil’s aura appeared before they swallowed — meaning swallowing isn’t required either.
That leaves putting it in the mouth as the key condition.
In Japanese, the barrel of a gun is literally written as “gun-mouth” (銃口 / jūkō). In English, the same word exists: muzzle — which comes from the Latin word for mouth (museau). So a gun can “eat” a Devil Fruit through its muzzle. That’s how Mr. 4’s gun Lassoo became an animal.
Swords Have a “Mouth” Too
What about Funkfreed, the elephant sword? In Japanese sword terminology, the opening of the scabbard is called koikuchi (鯉口) — literally “carp-mouth.” And a sword’s blade is written with the same kanji as “tooth” (刃/歯, both read ha).
Scabbard opening = mouth. Blade = teeth. A sword has more anatomy in common with a human mouth than a gun does.
What About Gel? (Smiley)
A blob of toxic gel has no obvious mouth. One theory: Caesar Clown — who can freely manipulate gas — shaped the toxic gel into a mouth-like form, causing the Devil Fruit to “perceive” it was being eaten.
This theory requires that a Zoan-type Devil Fruit has its own will — which the story later confirms.
Where Does the Ability Live in the Body?
Not the Heart — and Not the Consciousness
Law used his Ope Ope no Mi to transplant Smoker’s heart — and with it, Tashigi’s consciousness — into Smoker’s body. But Smoker’s Moku Moku ability stayed in his physical body. Tashigi’s mind couldn’t control it.
Conclusion: the ability resides in the physical body, not the heart or the mind.
Not Muscles or Organs Either — Probably DNA
Brook has no skin, flesh, eyes, or blood — yet he kept his Yomi Yomi no Mi ability. If the same logic applies to all Devil Fruits, the ability must reside in something Brook still has: bones, hair, or spinal fluid.
The simplest common denominator across all of these: DNA. (Alternatively, the Yomi Yomi no Mi may be a special case that resides in the soul rather than the body.)
The Bloodline Factor: Abilities Inherited Through Blood
Vander Decken’s ability was passed down through his bloodline — confirming that Devil Fruit powers can be inherited from parent to child.
If the ability lives in the DNA, it follows that blood and reproductive cells carry it too. When a parent dies, the ability likely transfers to the eldest child (the one carrying the oldest blood). This is what the story calls the Bloodline Factor.
The Fruit Detects the Host’s Death
When an ability user dies, a new Devil Fruit containing the same power appears in the nearest fruit. This was shown right after Smiley died at Punk Hazard — the ability transferred into a nearby apple.
Smiley’s case is worth thinking through carefully. A toxic gel was given a Devil Fruit and became a living creature with its own will. Even when parts of Smiley were burned off or split apart, the main body was still alive. But when a chemical reaction converted it from gel into gas — a state it could never revert from — the body was considered dead, and the ability moved to the nearest apple.
This gives us a definition of “death” for objects: the moment it can no longer return to its original state.
- A sword “dies” when it breaks
- A gun “dies” when it’s cut in half
And if Zoan-type fruits have not just will but actual life — that also explains why carnivorous Zoan users become more savage: the devil’s own aggression is layered on top of the user’s.
How to Steal a Devil Fruit Ability
One note before we begin: Moria’s shadows carry the skills of the person they came from (a swordsman’s shadow gives Luffy sword technique) — but Luffy’s shadow placed inside Oars did not give him the Gum-Gum ability. Devil Fruit powers don’t reside in shadows. After death, the ability lingers in the physical body for some time before transferring.
Blackbeard’s Method
My hypothesis for how Blackbeard does it:
- Target a recently-deceased ability user
- Use Black Vortex or Black Hole to extract the dormant ability from the corpse
- Direct the extracted ability toward a prepared fruit
- A new Devil Fruit is created
- Eat it
The exact scene hasn’t been shown yet — but given everything we know, this is the most consistent explanation.
Big Mom’s Method
The previous user of the Soul-Soul Fruit was Mother Caramel — also known as “the Mountain Witch who sold orphans.”
At her birthday celebration, Big Mom was overcome with joy at the sight of her favorite food — semla towers — and devoured everything within reach. When she came to, everyone around her was gone. The table and chairs were mostly gone. Only her bite marks remained.
Big Mom had eaten Mother Caramel, the orphans, and everything else. And after that, she could use the Soul-Soul ability.
Applying the DNA theory: Big Mom consumed Caramel’s body, taking her blood — and therefore her DNA — into herself. When Caramel died, the transfer condition was met: the ability moved to the being who had just ingested the user’s blood.
Momonosuke and Kaido: Why the Artificial Fruit Was a “Failure”
Vegapunk created an artificial Devil Fruit modeled on Kaido’s ability and labeled it a “failure.” Here’s why, based on this theory: Kaido cannot die.
Kaido’s introduction alone tells the story:
- 7 defeats in battle; captured by enemies or the Navy 18 times
- Tortured over 1,000 times
- 40 execution orders
- Hanged — the rope broke
- Guillotined — the blade shattered
- Impaled — the spears snapped
- Responsible for sinking 9 prison ships
- Nobody could kill him
The transfer condition requires the original user’s death. Kaido can’t die — so the ability in his DNA never triggers a transfer. Vegapunk couldn’t get the artificial fruit to fully “inherit” the real thing.
But when Kaido finally dies — the artificial fruit Momonosuke ate will complete. The failure becomes real.