The series centers on the life of Hideki Motosuwa, a held-back student attempting to qualify for university by studying at Seki prep school in Tokyo. Besides a girlfriend, he dreams of having a persocom : an android used as a personal computer, which is expensive. On his way home one evening, he stumbles across a persocom in the form of a beautiful girl with long hair lying against a pile of trash bags, and he carries her home, not noticing a disk fall on the ground. Upon turning her on, she instantly regards Hideki with adoration. The only word the persocom seems capable of saying is “chi” (??, Chii?), thus he names her that. Hideki assumes that there must be something wrong with her, and so the following morning he has his neighbor Hiromu Shinbo analyze her with his mobile persocom Sumomo. After Sumomo crashes during the attempt they conclude that she must be custom-built.