Chi (Elda), along with her sister Freya, were originally made by a scientist for his wife who wasn't capable of having children. Chi and Freya were persocoms, but were made to possess human emotion. This later backfired when Chi's sister Freya fell in love with the scientist. Aware of her situation, she kept her feelings to herself. Keeping her emotions inside proved to be too much for her, so it slowly began to destroy her. In a last ditch effort, Chi saved her sister by uploading her memories, personality, etc, into herself. This caused Chi to lose her own memories. Afraid that Chi would also fall in love with the scientist, he through her out.
One day, a young man named Hideki was walking home. On his way, he passed by Chi, who was wrapped and appeared to be thrown away. Seeing is as an opportunity to get his hands on a free persocom, Hideki grabbed her and fled. Unfortunately, she proved to be very heavy, so he had some difficulty. When he arrived at his apartment building, he struggled to figure out how to turn Chi on. He attempted to find her power button, but failed. Finally, with no other option, he decided to try one last place. Just as he reached for her private area, she awakened and seemingly began to glow. Upon her awakening, she looks at Hideki and says "chi". Hideki soon found out that Chi had no memory or knowledge of any sort, so he took it upon himself to teach her. Since she was only capable of saying "chi", Hideki chose to name her that. Soon Chi and Hideki meet a boy named Minoru Kokobunji, who attempts to help Hideki by scanning Chi's data with his own persocom. This attempt fails, so he tries using multiple persocoms at the same time. This causes Minoru's persocoms to simultaneously crash and fail. Minortu comes up with a theory that Chi is actually a legendary persocom known as a "chobit". One day, Hideki and chi go shopping. While they're out, Chi sees a childrens picture book called "A City with No People". A little while later, Chi begins having memories of a persocom identical to herself. It later turns out that these memories are of her twin sister Freya. It's also revealed that Chi's mother and Hideki's landlady, Chitose Hibiya, was the one writing the books for Chi. At the end of the series, Hideki admits his love for Chi.
At the beginning of the series, Chi has no knowledge of how to act in public or talk. All she was able to do is say "Chi". She would often misinterpret things Hideki tried teaching her. When he told her his name, she thought he was referring to his pornography. As the series progresses, Hideki teaches her manners, how to talk, and how to act in public.