In the future, personal computers have developed into "Persocoms", mobile computers that look like human beings. Hideki Motosuwa, a prep school student, desperately wants to buy a Persocom but cannot afford to. One day he finds a Persocom that has been thrown away and decides to keep it. When he turns on the Persocom, all she can say is "Chii" so he decides to name her that. After a while it starts to become apparent that Chii is more than an average Persocom. Having much better performance, it seems that Chii might be a "Chobit", a type of advanced Persocom rumored to have independent thought.
Naota is a normal Japanese 6th grade boy (although a little cynical), but when his older brother leaves for America to play baseball, his brother leaves his 17 year old girlfriend Mamimi behind. Mamimi is sending mixed signals and advances to Naota, and he doesn't know what to do about her. But to make matters worse, Naota's world is totally turned upside down when he is run over by a woman on a Vespa. During their first encounter, she hits him over the head with her guitar, which then causes a horn to grow out of his forehead. She calls herself "Haruko" and her presence changes Naota's life to even further insanity.
In their closed-off underground village, Kamina and Simon chafe at the limits imposed by the village elder. Yet all this will change, when Simon stumbles across a fantastic device—just as the village's peace is broken by a violent intrusion.
A dream of falling from the sky...and then birth. Rakka is born from a large cocoon into the Old Home, greeted by a group of females with small wings on their backs and shining halos above their heads. Soon Rakka's own wings grow, a halo is placed on her head and she is told that she must work in the nearby town of Grie. She soon realizes that the town and the entire world they live in are confined behind the Wall, a tall, impenetrable wall that none except the mysterious Toga are allowed to exit.
Himari Takakura passes away after going out on a trip with her brothers, twins Kanba and Shōma. She was, however, miraculously saved by a spirit in a penguin-shaped hat. In return for her extended life, the twins must search for an item known as the Penguin Drum with the aid of three penguins, which are visible only to the siblings.
After experiencing a bizarre dream, Madoka Kaname, a kind 14-year-old girl, encounters a magical creature named Kyube. Madoka and her friend Sayaka Miki are offered the opportunity of gaining magical powers if they agree to make a contract with the strange little being. He will also grant them one wish, but in exchange they shall risk their lives by accepting the responsibility of fighting witches. Invisible to human eyes, witches are catalysts of despair in the areas they inhabit. An ally of Kyube, a magical girl named Mami Tomoe, befriends and encourages the two girls to accept the contract. For an unknown reason, another magical girl named Homura Akemi is determined to prevent Madoka from accepting the deal.