What is Seastone?
Seastone is an extremely rare mineral found in the One Piece universe, extracted directly from the heart of the Grand Line in the country of Wano. The most distinctive feature of this stone is its ability to store the energy of the sea. Just as seawater neutralizes Devil Fruit users, Seastone carries this power, weakening them. However, this is no ordinary stone. Its density and durability are so high that only master craftsmen from Wano can process and shape it.
The uses of Seastone have expanded over time, becoming a strategic resource not only for pirate hunting but also for engineering and weapon technology. Major powers like the Marines use Seastone not only to neutralize Devil Fruit users but also to keep them under control. Therefore, the existence of this stone is a critical factor that affects not only individuals but also political balances.
The Geopolitical Power of Wano Country
Since raw Seastone is only mined in Wano, this country has become the owner of one of the world's most strategic resources, whether it wants to or not. Wano's secret export of Seastone is one of the main reasons Kaido chose this place as his base. This stone has increased not only the country's military power but also its global value.
Sea Stone Shackles and Weakening Mechanism
Seastone shackles do not directly neutralize Devil Fruit users; instead, they suppress their powers while weakening their muscles. Interestingly, users do not completely lose consciousness; they remain conscious but physically defenseless. This is a strategic advantage the Marines use to capture them alive.
The Rare Use of Seastone Bullets
A rarely seen detail in the anime and manga: bullets made from Seastone. These not only cause physical damage but also temporarily disable Devil Fruit users' powers. However, their production is so difficult that they are only used by exceptional individuals—such as Smoker's special weapon.
The Origin of Smoker's Jitte
Vice Admiral Smoker's Jitte, which he always carries, is a special weapon with Seastone tips. This weapon allows him to solidify the bodies of Logia-type users and physically affect them. If it were an ordinary jitte, Smoker would be nearly helpless against enemies like Crocodile.
Prison Systems Made with Seastone
High-security prisons like Impel Down use Seastone flooring to eliminate the possibility of Devil Fruit users escaping. These stones, embedded in the floors or walls, keep prisoners constantly weakened. This system is a much more permanent and passive form of control than traditional shackles.
Seastone-Equipped Ship Technology
The lower sections of marine ships are equipped with Seastone panels. This prevents sea creatures like the Sea King from approaching these ships. Since this stone reflects the natural energy of the sea, these creatures perceive it as part of the sea itself. This is a revolutionary invention in terms of maritime security.
Seastone's Neutralizing Property: The Only Weapon Against Logia
Logia users are normally immune to physical attacks. However, when they come into contact with Seastone, this “invulnerability” is nullified. For example, characters like Portgas D. Ace or Enel can sustain physical damage like ordinary humans when they touch Seastone.
Production Difficulty and Craftsmanship
Seastone is an extremely hard and high-density material, making it only processable at a microscopic scale using specific techniques. Wano craftsmen have been passing down these techniques for centuries, using them to carve the stone into shackles, nails, or weapon tips. This craftsmanship allows the stone to retain its effects while enabling it to be used in various forms.
Potential Unknown Side Effects
While the effects of Seastone on Devil Fruit users are well-known, the long-term effects of prolonged contact with the stone on ordinary people remain unclear. Some speculations suggest that the stone absorbs “life energy” and that prolonged contact may suppress the immune system.
CP0 and Seastone Equipment
Members of CP0, the World Government's most secret and deadly unit, can carry weapons coated with Seastone for special missions. This detail is rarely emphasized, but it is known that Seastone provides a significant advantage in high-level intelligence operations where physical contact is required. It is indispensable for silently neutralizing Logia-type targets.
Vegapunk's Seastone Research
Vegapunk studied Seastone's energy transmission properties and attempted to use this stone in some components of Pacifistas. His primary goal was not merely to suppress Devil Fruit users but to redirect this energy and use it as a weapon. However, the stone's density and limited availability prevented this technology from becoming widespread.
Seastone's Density Similar to Marble
Seastone is found in nature with a crystal structure nearly as hard and dense as marble. However, unlike ordinary stones, it resonates with sea energy, making it shapeable only with special diamond-tipped cutters and traditional metalworking methods. This makes it not only rare but also “untouchable.”
The Reaction of Marine Life to Seastone
Massive sea creatures like Sea Kings become agitated or suddenly change direction when they come into contact with Seastone. Some marine scientists argue that this stone emits a “natural signal that resonates with the sea,” triggering an instinctive flight response in these creatures. This biological effect is the primary reason why marine vessels remain unharmed.
Political Reasons for Seastone's Limited Distribution
The World Government deliberately restricts Seastone to specific regions because its widespread use could disrupt power balances, especially among the general population. Even ordinary people could use this stone to subdue powerful pirates, weakening authority. For this reason, the production chain is strictly controlled.
The Effect of Seastone on Devil Fruit Types
Paramecia, Zoan, and Logia types are affected differently by Seastone. While Logia users' physical forms are completely suppressed, Zoan users are generally unable to transform and their animal instincts are temporarily neutralized. This distinction has led to the creation of special protocols for how the stone should be used in Marine strategies.
Kaido's Capture with Seastone Chains
The fact that even an indestructible character like Kaido can be restrained by Seastone chains is one of the most striking examples of the stone's power. The scenes in Wano where Kaido is chained up serve not only to demonstrate physical restraint but also to create mental pressure. This is because the stone not only weakens abilities but also erodes motivation.
Seastone and Invisible Contact Technology
Wano craftsmen can embed Seastone in transparent layers within certain combat equipment to create an invisible contact effect. Thanks to this technique, enemies weaken without even realizing it. This method, developed specifically to counter Katakuri's Observation Haki, is said to have been tested as an unknown tactical weapon.
The Use of Seastone in Continent Exiles
Some high-profile pirates are held not in central locations like Impel Down but on isolated islands near Seastone mines. In these regions, the natural energy emitted by the stone creates a constant passive power pressure. This serves as an external control system for the prison, and prisoners never even consider escaping for years.
The Seastone Replica Problem
Many pirates and merchants have attempted to make a fortune by selling counterfeit Seastone products. However, fake stones not only fail to produce the desired effect but can also create a false sense of security, leaving pirates vulnerable to attack. For this reason, the Marine prohibits the use of Seastone except in officially stamped equipment.