Hideki had always dreamt of having his very own persocom (and of course, a girlfriend). Persocoms are extremely expensive and thus he is unable to buy one. But luck is on his side – one day, when he was on his way home, he notices a beautiful female persocom lying among the trash bags. And so Hideki made his way home carrying an abandoned persocom.
After the persocom had been turned on, she did not seem to be able to remember anything, and was only capable of saying “Chii”. Hideki names her that, and their adventure begins! How will Hideki teach her the ways of a human being, since she is unable to remember anything at all (which also means that she can’t even complete simple daily tasks properly)? How will both Hideki and Chii manage their relationship between each other? Chii is after all, a persocom, but she looks exactly like a human!