Episode 24 - Diffusion
Faced with the Doppelganger's giant monster, Mikoto starts pulling massive quantities of iron sand from the ground. Lifting herself into the air, she shapes it into a towering monster of her own, and the two titans clash.
Challenging Mikoto to protect the city if she can, the Doppelganger uproots several fuel tanks and starts hurling them in all directions. Using her iron sand monster, Mikoto manages to smash them all before they can do any damage. However, doing so throws large clouds of iron sand into the air, whence the wind spreads it across the sky... revealing the location of the hidden airship the Doppelganger was searching for.
The Doppelganger collapses her monster, and in its place starts forming hundreds of apparent duplicates of herself. As she does so, Mikoto briefly glimpses innumerable filaments of some unknown material shooting upwards. Moments later, a giant fleshy form rises into the sky and grabs hold of the airship.
Riding in on a motorbike, Ryoko Kuriba shows up and asks to speak with the Doppelganger. Saying she'll listen, the Doppelganger seizes Kuriba and rises up towards the airship. Mikoto, still wondering about the strange filaments she just saw, lifts herself up on a pillar of iron sand to give chase.
As they arrive on the roof of the airship, Kuriba says she believes she can find a way to eradicate a soul within two more months. She asks to be given the chance — so that she can use it on herself, and allow the Doppelganger to take over her body. The Doppelganger replies that she has no interest in a body — she wants to eliminate Kuriba in order to destroy the knowledge of how she was created. She says that if Kuriba really wants to help her, she should give up her life right now. Saying she's already accomplished what she wanted — develop the technology to save her mother — Kuriba spreads her arms and allows the wind to blow her off the airship. Mikoto sees her fall, but is unable to track her in the dark sky. However, Leader, having found herself unwilling to just walk away, has been monitoring the situation and mobilizes Scavenger to catch Kuriba in the air.
Meanwhile, the chief scientist from the Doppelganger's research institute is pleading with the city's higher-ups to stop them from destroying the airship. The Scavenger girls come down to land near the institute, and he notices the unconscious Kuriba with them.
As she climbs up to the airship, Mikoto gets a call from Shokuhou, who has been going over Kuriba's research papers. They compare Mikoto and Leader's observations with information Shokuhou has found on Kuriba's research into artificial muscles. Putting the facts together, they realize the Doppelganger is using some kind of self-replicating muscle tissue based on the properties of slime molds, which can burrow into materials at the microscopic level and control them. If true, it means that what looks like the Doppelganger possessing objects with its "soul" is actually an elaborate ruse.
Reaching the airship, Mikoto confronts the Doppelganger, who admits her bluff and reveals that she's growing huge quantities of the artificial tissue. She says she will use it to devastate Academy City and take revenge against humanity. Attacking with masses of the stuff, she briefly throws Mikoto off the airship's roof. Mikoto manages to avoid falling, and levitates back up to find herself confronted with multiple fleshy duplicates of the Doppelganger.
With help from Leader, who is watching the battle with her ability, Mikoto dodges attacks from every direction, while the airship tilts sharply back and forth. Finally, the real Doppelganger aims a massive attack at Mikoto, who barely manages to evade it. Grabbing one of her coins, Mikoto fires off a railgun... and the Doppelganger simply stands in place and closes her eyes.
Tropes
- Batman Gambit: The Doppelganger deliberately provokes Mikoto into attacking with her iron sand puppet, realizing it would scatter the sand throughout the sky and allow her to detect the cloaked airship.
- Bishoujo Line: Throughout the previous episodes, the Doppelganger has been absorbing more and more material, her body becoming progressively less human-looking as it does so. Here, after constructing her Kaiju form around herself, she emerges from inside looking almost completely human again note . What's more, her patchwork complexion and two-toned hair are gone, replaced with smooth golden-brown skin and pure ash-blonde hair. She has also clothed herself in a rather revealing white, flowing robe, making her look something like a goddess from classical mythology.
- Pet the Dog: Leader decides to come back and help Mikoto and Kuriba, even though Scavenger has technically completed its mission. It's implied to be because Mikoto was friendly and kind to her, which is not something she experiences much.
- Power Misidentification: It turns out the Doppelganger was faking the whole "soul possession" phenomenon, by using artificial muscle tissue combined with self-replicating slime molds to invade and manipulate objects.
- Stealth in Space: Or an atmospheric version — the research institute's airship flies around high above Academy City, concealed by a cloaking device. However, it emits a faint magnetic field, which allows the Doppelganger to detect it once the sky is filled with particles of iron sand which are affected by said field.
- The Reveal: We find out what else the Doppelganger was doing at the abandoned DNA lab besides obtaining her artificial skin: cultivating the special muscle tissue she's subsequently been using to control matter around her. As such, the "soul possession" phenomenon is shown to be a hoax which the Doppelganger is using as a smokescreen.
- Xanatos Speed Chess: The Doppelganger shows a knack for shifting strategies to take advantage of the rapidly-changing situation. When prevented from using the radar facility, she observes how Mikoto is able to use iron sand, and immediately provokes her into filling the sky with large amounts of it — revealing the airship that way. Next episode, it will be revealed that she is also carefully arranging matters such that either Mikoto or Academy City's defenses will be forced to destroy both her and the airship.
