Kamijou Touma is a student living in Academy City, a highly advanced place in terms of technology. Despite being gauged as a level zero esper (no powers), he possesses on his right hand the Imagine Breaker, an ability that negates any power whatsoever. Touma finds a young girl named Index who is trying to run away from Necessarius, a powerful magic organization that she is member of. Blessed with the skill of memorizing any sort of information, she holds 103,000 forbidden magical books within her head. As science and magic cross paths, Touma must face several dangers amid espers and magicians who appear at the exciting scientific town.
The Diclonius, a mutated homo sapien that is said to be selected by God and will eventually become the destruction of mankind, possesses two horns in their heads, and has a "sixth sense" which gives it telekinetic abilities. Due to this dangerous power, they have been captured and isolated in laboratories by the government. Lucy, a young and psychotic Diclonius, manages to break free of her confines and brutally murder most of the guards in the laboratory, only to get shot in the head as she makes her escape. She survives and manages to drift along to a beach, where two teenagers named Kouta and Yuka discovers her. Having lost her memories, she was named after the only thing that she can now say, "Nyuu," and the two allow her to stay at Kouta's home. However, it appears that the evil "Lucy" is not dead just yet...
After Medaka Kurokami defeated Myouri Unzen (the head of the disciplinary committee), she is recruited by the headmaster to join the "13 Party" - an elite and select group of 13 Abnormal students from Class 13. Medaka discovers that they are taking part in the Flask Plan, which aims to create perfect humans by sacrificing all the students in the school. It is up to Medaka and the rest of the student council to stop it.
Lain Iwakura appears to be an ordinary girl, with almost no experience with computers. Yet the sudden suicide of a schoolmate, and a number of strange occurrences, conspire to pull Lain into the world of the Wired, where she gradually learns that nothing is what it seems to be... not even Lain herself.
Steins;Gate is set in the summer of 2010, approximately one year after the events that took place in Chaos;Head, in Akihabara. Physical locales of Akihabara like the Radio Kaikan building can be spotted in the game. According to Chiyomaru Shikura, who headed the planning of Steins;Gate, Akihabara was chosen because it is an easy place for acquiring hardware parts, which makes it the ideal place for people interested in inventing and tinkering with things. The notion of time and time traveling are the main themes of the game. The concept of cause and effect is featured prominently in the game as the protagonist travels back in time numerous times to perform different actions in an attempt to alter what has happened in the future.