In the near future, computers can do practically anything. With the invention of persocoms - walking, talking, human-shaped robots that can do everything from logging on to the Internet, storing all kinds of data, displaying pictures and videos when hooked up to a TV, and having memories and a personality exactly as their owner wants them to - it's no wonder that everyone has begun to spend more time with their persocoms than with each other. Everyone except Hideki Motosuwa, a 19 year old bus boy who's struggling to get into college, and struggling even more with his expenses. After moving from his hometown of Hokkaido to the big city of Tokyo, Hideki is amazed at how many people have persocoms, and how much the persocoms can do. He knows that he could never afford one but one day, while walking home from work, he discovers a deactivated persocom in the garbage! Even though he's totally computer illiterate, Hideki takes her home and manages to get her to work again. At first, all she can say is "chi"(which is what Hideki decides to name her), but it seems that she has lost all memories of what happened to her before Hideki found her. Not only that, no one knows what kind of model Chi is, who made her, nor what kinds of things she's capable of. Not even Hideki's best friend Shimbo and the persocom expert Minoru Kokubunji can't find any information on Chi. They begin to believe that perhaps Chi is one of the Chobits, legendary persocoms that nothing much is known about, but are said to have powers and abilities that no other persocom has. In spite of the mystery that surrounds her, Chi is incredibly cute and sweet, but also very naive. Like a young child, she knows nothing of the world, so Hideki decides to keep her and try to teach her as much as he can.

As time passes, Hideki finds himself growing more and more attached to Chi. And it seems that Chi's feelings for Hideki grow as well - she tells Hideki that she's happy when he's happy, she's sad when he's sad, and she even offers to get a job so that he can get some extra money. Hideki is touched by all this, but deep down he knows that Chi is only acting this way based on her programming - no matter how human she may look and act, she's just a machine, and her actions are based on a bunch of "1s and 0s" so to speak, not on true emotions. Even so, Hideki can't help but feel that Chi is different from other persocoms, and she becomes much more than a household appliance to him. But as Hideki's bond with Chi begins to strengthen, he discovers that although persocoms are supposed to be a source of pleasure and convenience for people, they have caused many people suffering as well. The husband of his teacher Ms. Shimizu spent all his time with his persocom instead of her - at one point he forgot about her entirely and locked her out of the house. Mr. Ueda, the manager at the bakery where Chi works, actually fell in love with and married his persocom. But it wasn't long before she began to lose her memory and break down - however, in spite of this, she sacrificed herself to save him from a speeding car, leaving him totally distraught and heartbroken. Yumi, Hideki's coworker, fell in love with Mr. Ueda soon afterwards, but after finding out that he had been married to a persocom, she developed an extreme complex and felt that a human girl like her could never compete with a "perfect" persocom. Even Minoru, who had lost his sister whom he was so close to, made his own persocom Yuzuki, to look and act just like her. But even that failed to fill the void he felt.

After hearing all of these stories about the troublesome relationships between people and persocoms, Hideki begins to wonder and worry about his relationship with Chi - he knows she's not a living thing with feelings, yet he can't deny that he feels strongly towards her. Not only that, but more than once Chi has shown mysterious abilities that no one could explain - she's caused all the persocoms in the city to stop functioning and she was able to detect a persocom that didn't open a line to her. And also, unknown to Hideki or anyone else, Chi harbors another part of herself deep inside - an alter ego. It seems that this other part of her is trying to guide Chi into finding the "someone just for her." What is this exactly, and does Chi really have the emotions to find and love this person? Is Chi really a Chobit? Have Chobits crossed the line between man and machine and actually gained possession of real feelings? And what other mysteries surround Chi and the strange bonds that people and persocoms share? Whatever the answer is, Chi and Hideki must come to grips with their own feelings before Chi falls into the wrong hands and her true power is unlocked!