Lucy is a special breed of human referred to as "Diclonius," born with a short pair of horns and invisible telekinetic hands that lands her as a victim of inhumane scientific experimentation by the government. However, once circumstances present her an opportunity to escape, Lucy, corrupted by the confinement and torture, unleashes a torrent of bloodshed as she escapes her captors. During her breakout, she receives a crippling head injury that leaves her with a split personality: someone with the mentality of a harmless child possessing limited speech capacity. In this state of instability, she stumbles upon two college students, Kouta and his cousin Yuka, who unknowingly take an injured fugitive into their care, unaware of her murderous tendencies. This act of kindness will change their lives, as they soon find themselves dragged into the shadowy world of government secrecy and conspiracy.

Kai, who has powers different from the rest, together with his sickly sister Hikaru was protected by an organization called ASHURUM. Scouted by Eiji, Kai was delegated to the ASHURUM special force AESES and undergo intensive training. Whenever he was free, Kai visited Hikaru at the hospital belongs to the organization, but Hikaru's condition never improved. So, one year later, with amazing growth from the intensive training, Kai decides to escape from the organization. (Source: ANN)

After a routine raid, the rookie sky pirate Coud finds a most unusual cargo in his mates' cargo hold: Ren, an "Edel Reid", a race prized by humans for granting special combat power to their partners through "Reacting". He quickly discovers, however, that Ren is even more prized than he expected. The pirate ship is visited by three members of the Edel Reid Complete Protection Agency "Arc Aire", who try to purchase her. When Coud refuses, the ship is suddenly attacked by a mysterious force, and Coud's captain charges him with Ren's protection. (Source: ANN)

The student-filled Academy City is at the forefront of scientific advancement and home to the esper development program. The seven "Level 5" espers are the most powerful in Academy City, and ranked third among them is middle schooler Mikoto Misaka, an electricity manipulator known as "The Railgun." When strange incidents begin occurring throughout the city, she finds each crime to be connected to the elusive "Level Upper," a legendary device that allegedly increases the esper level of its user. As the situation escalates, it becomes apparent that there is more to the Level Upper than meets the eye, and that Academy City may be a far more twisted place than the glamorous utopia it appears to be. Toaru Kagaku no Railgun focuses on Mikoto and her friends—and the dangerous situations they find themselves in—as they get caught up in the matter of the Level Upper. As Mikoto says, "There's never a dull moment in this city."