Our protagonist is a poor student who rescues a 'persocom' from a trash heap. This device is created to make its owner happy – 'Chi' comes in the form of a beautiful 16-year-old girl, and is utterly obedient to her master's wishes. The book alludes to the fact that people have sex with these things, although CLAMP are more interested in the emotional effect of having these "perfect" simulations of humanity walking among us. Among the case studies in the book we find a guy who marries his persocom, another who tries to imbue his with the attributes of a deceased sister. And our protagonist is continually torn between romance with several pretty ladies and looking after his alluring new gadget.
The boys at Kraken recently discussed the (admittedly fatuous) question of whether you would make love to a robot. But the metaphor powering Chobits digs into the extent to which we already have quite powerful emotional (even physical) relationships with lifeless bits of kit. The distinction between sex with robots and internet pornography is already getting blurry. But the worry at the core of Chobits is deeper – will machines eventually replace other people in our social circle, to the point where we become cut off from humanity, with only androids in our orbit?
14.03.2016 edit to add:
Just finished the second volume, which ups the saccharine levels considerably, and becomes an apologia for people who prefer virtual girlfriends to the real thing. The (all-female) CLAMP team see no issue with men (and it does appear to be mostly men) who fall in love with meek, child-like automatons designed to service their every whim and desire. There are other problems with the book – the plot unravels completely at the end, to the point where the whole thing feels improvised. But drawing the wrong conclusions from an interesting opening scenario is unforgivable.