"Erosion" (浸蝕 Shinshoku?) is the 48th chapter of the Toaru Kagaku no Railgun manga series.
At her hotel, Misaka Mikoto is still worried about Misaka 10032, while some girls nearby mention Shokuhou Misaki (using her epithet "The Queen").
Mikoto heads out and hacks surveillance cameras, eventually finding footage of 10032 being taken away in an ambulance. She tracks down the fire station to which the ambulance belongs and finds the EMTs who drove it. She asks about 10032, claiming to be a friend of hers and keeping her own (identical) face hidden with a hat, and is told that she was brought to Heaven Canceller's Hospital. However, the hospital's receptionist claims that no student was brought in at that time. Mikoto goes back to the EMTs but they stick to their story. She becomes suspicious, since someone in a Tokiwadai uniform being brought to hospital should have led to the school being contacted. She asks about who the hospital worker who took in 10032 was, but the EMTs cannot remember. She then enters the ambulance and hacks its navigation system, discovering that the ambulance actually went to a parking garage (where 10032 was presumably transferred to another vehicle). She points out this inconsistency but her hat falls off, revealing her face to the EMTs. They mistake her for the girl they transported and one recognises her as a Level 5 with control over electricity, saying that she must have altered the navigation records. Mikoto grabs one EMT and demands that they tell the truth, but then realises that their memories were altered. She lets go when Anti-Skill arrives at the scene.
Meanwhile, Shirai Kuroko and Uiharu Kazari are going on patrol with Saten tagging along. Though depressed at having to stay in a different room from Mikoto, Kuroko notices that they are off their patrol route. A strange man asks them for help, claiming that he's a spectator from outside the city and has just been robbed. Misaki exploits this distraction to use her ability on the three girls from behind. The man, now revealed to be Keitz Nokleben, says that the stolen property was memories of Misaka Mikoto.
Back at the fire station, Watanabe has come to deal with Mikoto's incident and she apologises for her student's actions. She takes her away in a car and asks why she did this. Mikoto answers that she suspects Misaki of using her power to cover up a crime but admits she has no proof. Watanabe tells Mikoto that, since she is a Level 5 and the Daihaseisai is ongoing, she can't make any careless actions. They arrive at their destination and Watanabe asks Misaki's clique to watch over Mikoto. A telepath in the clique establishes a circuit with Mikoto that lets her track her location. As Watanabe leaves, it's revealed that she (and the driver of the car) are under Misaki's control.
Mikoto spots Kuroko and the others passing by. She calls out to them, planning to get their help investigating. However, they no longer remember being friends with Mikoto.
In order of appearance:
- Misaka Mikoto
- Misaka 10032
- Heaven Canceller (cameo)
- Saten Ruiko
- Uiharu Kazari
- Shirai Kuroko
- Keitz Nokleben
- Shokuhou Misaki
- Hokaze Junko
- Kobayashi Satori
- Electromaster (Railgun-variant) - Misaka Mikoto, Level 5
- Mental Out - Shokuhou Misaki, Level 5
- Telepathy - Kobayashi Satori, Level 3