Highlights
- The quirk-destroying drug, developed by the Yakuza, could permanently damage superpowers.
- The Yakuza planned to profit by selling fear and relief through the drug and its antidote serum.
- Eri's unique Rewind Quirk can reverse the effects of the drug, making her the ultimate antidote.
In the underground world of villainy in My Hero Academia's society, one creation sparked immense terror and promised tremendous profits: the quirk-destroying drug. Developed by the criminal Yakuza organization Shie Hassaikai and their merciless boss Kai Chisaki, also called Overhaul, this substance had the power to irreversibly damage an individual's quirk factor, destroying one's quirk permanently.
Through cruel experiments led by Overhaul and utilizing the unique rewind quirk of a young girl named Eri, the Shie Hassaikai cultivated a drug prototype delivered via specialized bullets that could temporarily disable quirks. With this testing phase showing promise, the drug was perfected to have lasting effects, and a matching antidote serum was developed for reversal, establishing a scheme where the Yakuza could dominate the black market and profit immensely from both selling fear in the form of the drug and relief in the serum to villains and heroes alike.
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Anime Debut | Episode 65, "Overhaul" |
Manga Debut | Chapter 125, "Overhaul" |
Effects | Completely destroys someone's Quirk Factor |
The Genesis of a Dangerous Discovery
Initial Experiments Using Eri's DNA
The origins of the quirk-destroying drug can be traced back to the genetics of a young girl named Eri. Eri possessed an extraordinarily rare Rewind Quirk that allowed her to reverse another person's biology back to a previous state. Seeing her potential, Kai formulated a sinister plan to utilize Eri's genetics to develop a drug that could target the quirk factor—the genetic mechanisms within a person's DNA responsible for their individual superpower.
Kai initially pitched the idea to his boss, the former leader of the Shie Hassaikai, but it was rejected due to ethical concerns. Kai then incapacitated his boss and took over the organization. Through collecting genetic material from Eri's body, which Kai could do through his own quirk, the Shie Hassaikai scientists were able to cultivate the first prototype drug that could temporarily damage a target's quirk factor for a few hours by disabling their quirk. Further testing and funding from an alliance with the League of Villains allowed the drug to be perfected, with its effects becoming permanent. Early prototypes were distributed solely for testing purposes.
Controlling the Black Market through Fear and Finance
Mass Production and Distribution of Bullets and Serum
With a completed formula in hand, Kai strategized to monopolize the illegal quirk-related black market. He mass-produced quirk-destroying bullets to distribute the drug, encasing hypodermic needles within distinctive red cartridges. Simultaneously, Kai's scientists developed an antidote serum that could restore quirks.
Kai's sinister plan was to sell the bullets to villains on lucrative contracts, dictating they could only be used against heroes. Once disabled, the heroes would pay tremendous ransoms to the Shie Hassaikai for the antidote serum. Through instilling mass fear across civilian and hero populations with the threat of permanent Quirk destruction, Kai aimed to establish the Yakuza's complete dominance over Japan's illegal markets and recover their lost influence.
To start off, we had to figure out how to preserve that effect…and it took quite some time.
To validate his product, Kai allied with the powerful villain group League of Villains, led by Tomura Shigaraki. During field tests against heroes, the bullets proved deadly effective, most notably erasing the great U.A. student Mirio Togata's Permeation Quirk in an explosive battle against Kai. With this demonstration, Kai secured the League of Villains commitment and funding to mass produce his coveted bullets and serum nationwide.
However, the heroes caught wind of Kai's sinister activities. Before his black market monopoly could be fully realized, agents of the My Hero Academia's Hero Public Safety Commission led a covert raid on the Shie Hassaikai hideout to intercept Kai's shipment of bullets and serum.
Eri: The Ultimate Antidote
Eri's Training and Mastery of Her Quirk
During the Paranormal Liberation War, erasure hero Shota Aizawa witnessed firsthand the permanent power of quirk-destroying bullets after being shot during his battle against Tomura Shigaraki. Forced to amputate his leg to halt the drug's spread, Aizawa realized Eri's Rewind Quirk could potentially provide a cure.
After her rescue from Kai Chisaki, Aizawa theorized that Eri's unique Rewind Quirk possessed the potential to rewind a person's quirk factor back to an undamaged state, reversing the drug's effects. If Eri could control her abilities precisely enough through training, she could overwrite the ravages of the drug.
Months of intensive training under Aizawa at U.A. helped Eri master her delicate power. In a landmark achievement, Eri demonstrated her ability was correct by completely restoring the erased quirk of former U.A. student Mirio Togata, now cementing her as the sole cure for the quirk-destroying drug's feared consequences.
Though Overhaul was defeated, remnants of his drug remained with the League of Villains under Tomura Shigaraki, who sought to weaponize the small reserve obtained from the Shie Hassaikai against heroes.
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Continued Impact and Adaptation
Garaki's Replication of Bullets
In an act of desperation, Shigaraki appealed to the renowned mad scientist, Doctor Kyudai Garaki, to replicate Kai's quirk-destroying bullets. Though exceedingly difficult due to their complex biological composition, Garaki's formidable scientific skills managed to produce a limited batch by analyzing Eri's DNA extracted from Kai's original research on the drug.
This allowed Shigaraki to target the heroes with the remaining bullets. In a chaotic hospital raid aimed at capturing Eri, he fired shots, critically injuring Erasure hero Eraserhead and forcing him to self-amputate his leg to stop the spread of the drug. The other bullet was exploded by Bakugo before it could hit Endeavor.
When most of Garaki's replications were melted by X-Less during the raid on Jaku General Hospital and Twice was unable to duplicate the bullets, Shigaraki was left without a consistent quirk-destroying arsenal. While Eri's developing control over her Rewind Quirk assured no victim of the drug would remain powerless forever, the bullets demonstrated how even marginalized traces of its sinister formula remained a doomsday weapon in the villain's hands.
While no longer actively distributed, the quirk-destroying drug demonstrated the grave dangers of illicit quirk experimentation. Its effects catalyzed changes in hero and villain societies and established strict ethical protocols for scientific experiments involving quirks in order to prevent weapons as dangerous as the drug from being created without oversight. Its legacy serves as a reminder of why protecting gifted children and upholding research standards must be top priorities in My Hero Academia's world.
My Hero Academia is available to stream on Prime Video.
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