Babylon City is a fictional place within the GetBackers manga series. It rests beyond Heaven's Gate within an adjacent universe, in another Shinjuku city. Unlike the Shinjuku that is seen throughout the series, the one in Babylon City is without the Infinity Fortress, and it is called the town of Creators.
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Babylon City is mentioned heavily throughout the series, but very little information is given until we reach the end of the manga. When Ginji Amano who is chosen as the King of Creation, walks through Heaven's Gate, as the rest of his world is erased, he enters Babylon City, and is welcomed by Dr. Kuroudo Akabane in Shinjuku without the Infinity Fortress. Akabane is a surgeon in this Shinjuku, and he takes Ginji to show him the truth.
Akabane shows Ginji the condition of Shinjuku which has remarkable differences from the one where Ginji comes. Here, the city is peaceful and thriving, the environment is cleaner, and the people work peacefully, although it's not all perfect since the gangsters and other problems are still around. Ginji somehow seems melancholic and Akabane who made this town.
In this Shinjuku, Ginji also meets Juubei Kakei and Kazuki Fuuchouin who are strolling together. Ginji calls Kazuki, but the latter doesn't recognize him. Akabane explains Kazuki here is a female. She is the daughter heir to the traditional Fuuchouin School of Japanese Stringed Instruments. Juubei is the successor to the Kakei School. He is a genius of acupuncture and is a lecturer at the college within the city. Akabane also mentions that Shido Fuyuki, Sakura Kakei, Haruki Emishi, and Toshiki Uryuu are also around. However, Ginji declines to meet them for they may also be different.
Akabane later takes Ginji to a cemetery. There Ginji meets a woman who visits his son's grave. This female scientist knows the secrets of Babylon City, and explains the story of creating another world where Ginji and his friends come.
She reveals the plan of creating a back-up world by involving many experts in their fields. They are called the Brain Trust. The scientists successfully established another world, but that new place gradually becomes out of control, therefore the Brain Trust decides to destroy it.
The Brain Trust relies on the Archive to format that world and choose a "creator" to re-establish that world again according to what the Brain Trust intends. Without telling the scientist that he is chosen person, Ginji simply explains that he loves the world that he knows of. In their conversation, the scientist also explains to Ginji that her reason to have this new world is to retrieve the life of his son. After listening to her story, Ginji takes his leave, and then he suddenly calls the scientist and joyfully addresses her as mother.