Shotacon is a sexual complex, comprised of attraction to underage (mostly below thirteen years) boys.
It’s female counterpart is lolicon, with an underage girl in the center of attention.
Interestingly enough, it is mostly females are interested in it, instead of homosexual men.
The shotacon phenomenon appeared in the 1980’s, first as an offshoot of the yaoi genre, and then it grew separately, as its own genre of erotic visual art.
At first, it consisted only of fanart, though now there are mangas and animes which are deliberately aimed at these themes.
With time passing, the complex became a bigger and bigger trend, amassing enough demand for the shota theme to become a major one in the hentai genre, though still not as widely spread as lolicon or tentacle adult entertainment, for that matter.
An entry was added to Urban Dictionary in 2003, already, with plenty of other definitions written since then.
Shotacon is associated with the phrase “ara ara” which is a kind of way to say “my, my” in Japanese.
It is mostly seen on memes, where two women surround an unsuspecting shota.