The Japanese abbreviation of the English phrase "Lolita Complex." The term refers to the book Lolita by Vladimir Nabokov, which describes an older man's illicit sexual affair with a twelve-year-old girl. Sometimes written as "roricon" or "rorikon" due to the inexact mapping between Japanese and English phonemes. Not so much an Anime Trope as a Japanese cultural trope, this is the term used to describe the fetish/fascination some mature people have for underage girls, particularly sailor-suited schoolgirls. There is an entire industry in Japan devoted to providing legal but schoolgirl-themed pornography, taking advantage of the cute childlike appearance some Japanese women maintain well into their twenties.
Because the characters in anime are often young by convention, many fans think that a character can only be Lolicon if she is twelve or younger. Exceptions are granted if the other character in the relationship is a lot older.
Lolicon themes are far more common in hentai material, but can still be found here and there in mainstream anime. One particular device used to skirt the boundaries of taste and legality is the exotic being (alien, creature of magic, robot or the like) which takes the form of an underage human girl, but is in fact for all other practical purposes an adult. Interestingly enough, Nabokov himself addressed the subject with far less sympathy and jocularity, describing said older man in his book as "a vain... cruel... hateful person." Nabokov's Lolita was also portrayed in a not very sympathetic light, as she consciously seduced him their first time to manipulate him, and was by no means unwilling or innocent in the affair.
Oddly enough, many idols among the fetish are from shoujo series intended for girls. However, this may have more to do with the innocent fetish the younger female audience has with having a cool older boyfriend. On the other hand, some Moe series tend to be more blatant in their aims.
The trope may have a slight Freudian Excuse, at least in anime; after WWII, the Japanese constitution was amended to outlaw all public exposure of adult genitalia (which of course in part led to the codification of Naughty Tentacles) or pubic hair, but not children's genitalia - making every female in Japanese entertainment retain prepubescent traits. It's just as lame as most Freudian Excuses, though.
- Maybe. One must remember that Humbert is an Unreliable Narrator, and is prone to projecting the way he wants things to be over what actually is. Even so, he admits that Lolita frequently cries herself to sleep, although he mischaracterizes the reason. See our page on the novel for more information.