In a society where personal computers called Persocoms closely resemble humans, the true nature of love is put to the test. Hideki Motosuwa, a young man from the countryside trying to pass his college entrance exams, struggles to make ends meet, making it impossible for him to afford the latest technology: Persocoms, which are humanoid computers. One night, on his way home, he stumbles upon an abandoned Persocom and decides to bring her to his apartment. When he activates her, she responds with only a single word, "Chii," which becomes her name. Unlike other Persocoms, Chii cannot download information, forcing Hideki to manually teach her about life as he studies for his exams.
With assistance from his friends, Hideki begins to investigate the mystery surrounding Chii, who might be a "Chobit"—a legendary type of Persocom rumored to possess genuine human emotions, thoughts, and the ability to love their owner. However, the potential for a romantic relationship between a Persocom and a human remains uncertain.