Automatic Purification System
The Automatic Purification System (自動浄化システム Jidou Jouka Shisutemu) is a phenomenon that occurs within a field, which prevents Magical Girls from becoming Witches in the universe of Magia Record, and releasing Doppels instead.
The field initially only surrounded Kamihama City. It was used to block all Kyubeys from entering, having them lose consciousness the moment they entered, with the exception of Lil' Kyubey, as it was separated from the Incubator network. The Doppel System prevents any Magical Girls inside from becoming a Witch, and allows for the manifestation of Doppels which release a lower amount of energy as compared to Witches.
The field was created by the combined efforts of Ui Tamaki, Nemu Hiiragi, Touka Satomi, and Alina Gray}}, it operates by collecting impurities from fully darkened Soul Gems directly, converting the energy therein to a usable form, and manifesting the user's Doppel. As the energy gains are forwarded directly to Kyubey, the APS thus contributes directly to the fight against entropy. As the system's core needs a viable inhabitant (such as someone involved with its formation, either Lil' Kyubey, or Ui), after Lil' Kyubey left it unattended, Kyubey was able to eventually take control of it due to its connection to Lil' Kyubey. Once it manifested, he was even able to teleport it to different parts of Kamihama to keep it out of others' reach.
The core of the APS is a conceptual space that can be accessed by bringing all eight Kimochi together. This space can be tied to a specific person, and the status of the APS is directly linked to the life of that entity, ultimately ending up with Iroha as host, as well as Ui, Touka, Nemu, Lil' Kyubey and Sakurako as inhabitants. If the core's host is taken out of commission (such as due to their life force being spread too thin across time), the APS may purify Soul Gems more slowly, and in the worst-case scenario cease to function entirely.
By the end of Arc 2, the Doppel System has been spread all across the world.
In the anime, it instead does not work correctly, causing Doppel use to eventually result in a glorified Witch-like state known as Doppel Syndrome. In Episode 24, it was shattered, but ultimately transferred to solely surround Iroha Tamaki as Ui's final gift to her, allowing her to use the Infinite form of Giovanna despite never becoming Infinite Iroha herself.
