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Diffusion (拡散 Kakusan?) is the 24th episode of Toaru Kagaku no Railgun T. It was broadcast on September 18th 2020. The episode was directed by Tanaka Tetsuro, Ranzaki Akari and Mori Yoshihiro, the screenplay written by Yasukawa Shogo, and storyboarded by Iida Takashi and Nagai Tatsuyuki.

The Doppelganger changes into a massive form by gathering debris through "soul possession". With the massive beast and its overwhelming mass standing in her way, Mikoto creates an iron sand colossus against it. By taking advantage of the properties of iron sand, Mikoto slowly breaks down the Doppelganger's creation, while the Doppelganger fights back by trying to send fuel tanks crashing onto the nearby urban area.

Mikoto was barely able to defend herself against the fuel tanks exploding in mid-air, but the Doppelganger's actions not only enable her to turn Mikoto's attacks against herself; it also exposes the location of the stealth airship that stores the backup data of the research facility. Meanwhile, Kuriba heads towards the origins of the Doppelganger to settle things once and for all.


Mikoto is taken by surprise as the Doppelganger gathers a large amount of debris to create a massive creature of stone that can withstand Mikoto's attacks. The Electromaster, amazed to experience an enemy that forces her to go all out, decides to return the offer by amassing iron sand from the surrounding ruins and shaping them into a massive iron sand puppet. Shortly after, the Doppelganger continues her attacks on Mikoto, who discovers how her iron sand fails to penetrate the debris surrounding her enemy. Upon seeing the fragility of the iron sand puppet, the Doppelganger decides to deal the finishing blow. But, this exposes the debris creature to an iron sand bullet attack prepared by Mikoto.

The Doppelganger quickly attempts to recover from the iron sand bullet attack that destroyed part of the debris creature's torso, but soon notices that iron sand has mixed with the surrounding debris, compromising its durability. To compensate, she resorted to a series of diversionary attacks by tossing filled fuel tanks into the air, exposing the nearby neighborhood into danger. Mikoto is forced to destroy the fuel tanks using her iron sand bullets, oblivious to the Doppelganger's plans to use the iron sand to expose her true target.

The clash between the two giants can be heard from as far as School District 7, where Saten heard the explosions from her home while sharing a meal with Uiharu and Kuroko anxiously waits for Mikoto's call from inside Tokiwadai Dormitory. Meanwhile, Kuriba Ryouko rushes to the scene of battle on a motorcycle.

The clash enters a momentary lull when the Doppelganger creates countless copies of herself using debris from her massive creation. Then, an almost invisible material emerges from the backs of each of the debris clones in a split second, forming a massive construct that looks like the Doppelganger. This construct then holds on to its real target, the data backup stealth airship used by the research facility that "produced" her. Shortly after, Kuriba Ryouko arrives and rushes to propose something to the Doppelganger, prompting the latter to take her to the top of the airship. Mikoto, seeing Kuriba being taken by the Doppelganger, is forced to look for a way to reach the airship from the ground.

Mikoto, while en route to the stealth airship using a length of iron sand, realizes that her clash with the Doppelganger was a means to locate the airship. Although uncertain of the Doppelganger's true objective, Mikoto focuses on rescuing Kuriba. Meanwhile, the Doppelganger spreads its control into the airship and provides an opportunity to listen to Kuriba's proposal: to give the latter two months for Indian Poker to produce a way to remove a person's soul, specifically that of Kuriba herself. The Doppelganger quickly rejects her proposal, aware that it is illogical and, even if was possible, may be used against her instead. Moreover, the Doppelganger is nonetheless willing to kill the original as the former plans to bring down Academy City herself. But, Kuriba instead decides to do it herself by letting herself be caught in the strong winds surrounding them.

As Kuriba Ryouko plummets to the ground, Mikoto, who was still making her precarious climb to the airship from a dangling "vine" of material produced by the Doppelganger earlier, fails to reach the original using her iron sand. Scavenger eventually becomes informed of the situation due to the communication device attached to Mikoto and makes a combined effort to locate and safely intercept Kuriba. Then, after planning to return Kuriba to the facility, Leader informs Mikoto of the Doppelganger's current location.

Shokuhou Misaki contacts Mikoto as she looks into Kuriba's studies before the fateful cyborg experiment, and Mikoto reveals that she has a hunch that artificial muscles may be used by the Doppelganger, although the sheer scale of how the Doppelganger uses it leaves her uncertain. With the help of Leader's quick research, they discover that the Doppelganger indeed uses artificial muscles, but with the traits of ant parasites and slime mold. The Doppelganger was able to use them to such an extent through a combination of Kuriba's intellect and the computational speed of a machine.

After being informed of the truth behind the concept of "soul possession", Mikoto confronts the Doppelganger, whom she thinks is in despair after realizing that she was not human. The Doppelganger reveals her plan to take "revenge on humans" by killing Kuriba Ryouko and then using the artificial muscles under her control to detonate 20 fuel tanks below them, with the intention of setting Academy City on fire. Afterwards, the Doppelganger once more begins her attack by sending decoys of herself to Mikoto before forcing the airship to list to its side in an attempt to throw out Mikoto from the airship. This however fails due to Leader informing Mikoto of nearby threats. Then, as Mikoto regains a foothold on the airship, a massive drill-like construct comes rushing towards her, forcing the Electromaster to fire her Railgun, catching the Doppelganger in its path.

Adapted From

Major Events

  • Misaka Mikoto and the Doppelganger's confrontation culminates into a "battle of giants" with Mikoto's iron sand puppet facing the Doppelganger's debris monster.
  • The Doppelganger locates the airship that stores the backup data of the research facility that "produced" her with the use of iron sand spread by Mikoto as a result of their clash.
  • Kuriba Ryouko confronts her Doppelganger and presents a proposal enabling the erasure of the original's soul so that the Doppelganger can take the original's body. The Doppelganger ultimately rejects the proposal, but is willing to kill her original regardless.
  • Kuriba Ryouko is rescued by Scavenger after she fell from the airship during the failed negotiation with the Doppelganger.
  • The battle between Mikoto and the Doppelganger appears to come to an end as Mikoto fires a Railgun with the Doppelganger in its path.


By order of appearance:




  • The iron bridge seen in previous Toaru seasons (prominently in the Sisters Arc) is briefly seen in this episode, when Mikoto blast the first gas tank raised by the Doppelganger.


  • Kuroko remembers Mikoto's promise that she will call her if anything comes up back in Railgun T Episode 21.[1]
  • Scenes from the three previous episodes are used as flashbacks, when Leader explains to Mikoto and Misaki on how the abilities of the Doppelganger work.[1][2][3]

Cultural References

  • The Doppelganger tricked Mikoto on using iron sand bullets onto the tanks. This caused the iron sand in the atmosphere to generate a magnetic field and stick onto the airship, with charged particles from solar winds affecting it. This explains why the Doppelganger be able to detect the otherwise invisible airship with her eyes that detects magnetic fields.
  • The Doppelganger references Cinderella, a story of a simple girl who becomes a princess by magic, where it only lasts till midnight. Here in this episode, the Doppelganger compares the airship to the aforementioned princess, and the iron sand to the expired magic that reveals its true form.
  • Slime mold is an informal name given to several kinds of unrelated eukaryotic organisms that can live freely as single cells, but can aggregate together to form multicellular reproductive structures.
  • According to Railgun manga editor Ogino Kentarou, the two things that the Doppelganger based her artificial muscles on are Ophiocordyceps unilateralis and muscles of a gorilla.[4]
    • Ophiocordyceps unilateralis is a fungus which infects ants, becoming a parasite that eventually grows enough to burst out of the ant's carapace and take over its brain, controlling the ant like a zombie until it dies, after which the fungus uses the corpse as nutrition to spread its spores.
    • A gorilla has gut bacteria that allows it to digest cellulose, a compound extremely common in plants, which provides its muscles with enough energy to maintain its strength even without heavier foods, the reason why the muscles of a gorilla are super strong.

Differences in Adaptation

  • Due to censorship reasons, the Doppelganger already had white-threaded clothes when she appeared out of the 'giant puppet' in this episode. In the manga, she was still naked at that time until she gained these clothes at the airship.[5][6]
  • The adaptation cut a scene of Ryouko from the manga where she sent a basic design of the cyborg to the chief to save her mother.[5]
  • Scenes of Saten and Uiharu mistaking a tank blown by Mikoto as fireworks, as well as Kuroko humping on Kill Bear are anime-original.

Kuriba's scooter in the manga.

  • In this episode, Ryouko used a motorcycle to chase down the Doppelganger. Originally, she used a scooter.[6]
  • Naru's paper jet used a ramp to launch itself into the sky, unlike in the manga where they flew away immediately without a ramp.[6]
  • Mikoto did not fall off the airship in the manga.[7]

Animation Trivia

  • At least 25 seconds of footage from the previous episode is reused in the beginning of the episode before actual original scenes for the episode are seen.[3]
  • Both the giant puppet created by the Doppelganger and the iron sand puppet created by Mikoto are rendered in CGI.
  • The pose of the iron sand puppet where it fired an iron sand bullet, in one of the shots, resembles the pose that Misaka Mikoto does when she fired her Railgun back in Railgun Episode 1.[8]

Unanswered Questions

  • Who is the person that the chief talked with?
  • Did Mikoto finally defeat the Doppelganger?


# Title Time Scene & Notes
Kagaku no Hatten to Gisei The giant puppet attacks Mikoto, Mikoto creating an iron sand puppet to counter the Doppelganger's[9]
dual existence Opening
Kaminara me Mi nite Mikoto's iron sand puppet vs the doppelganger's giant puppet[9]
Saa, jikken o hajimeyou Mikoto destroys one of the gas tanks that the Doppelganger has launched[9]
Unverified Track The Doppelganger finally found the airship
Joshi-ryoku Zenkai-sen! The Doppelganger takes Ryouko to the airship[9], Part 1 End
Tenpu Yumeji Part 2 Start, Ryouko talks her proposal to erase her soul to the Doppelganger[9]
Time Limit Scavenger save Ryouko from falling in the sky[10]
Shinka no Kaidan Mikoto sensed something wrong on Ryouko's 'soul possession', Leader explains the real nature of the abilities of the Doppelganger to Mikoto and Misaki[9]
Unverified Track Mikoto confronts the Doppelganger at the airship
Nande Koko ni Misaka Mikoto ga irundaaaa!?!? Mikoto battling the Doppelganger[9]
Aoarashi no Ato de Ending
Unverified Track Preview



This section requires expansion
  • Misaka Mikoto: "The soul diffuses and possesses stuff? Is that what that colossal monster-like thing is? Could there be anything more dodgy than that?"
  • Shokuhou Misaki: "People tend to believe in what they want to believe. Like Indian Poker cards that make you bust grow bigger."
  • Misaka Mikoto: "You're bringing that up again?!"[3][11]



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