As I grewthrough adolesence, I've always had a slight craving for human flesh, I just didn't consciously recognize it until a few years ago. I had always written it off as a craving for meat.
My interest in cannibalism was spark by two sources:
The first was when I was in English Lit in my junior year of high school; we were discussing Walt Whitman's Leaves of Grass. I can't remember the exact poem, but the teacher talked about how the atoms and molecules from fallen people became part of the soil and then were absorbed by plants. I can't remember if he submitted the idea himself or if I came to the conclusion, but afterthinking about it that way one could almost consider that their souls joined the the plants. It made me wonder, if souls do exist, if eating the flesh of someone would join their spirit with your own. The notion was further spurred on by various vampire fiction, where the memories of the victims (and sometimes their souls) would join with the vampire. (Such is in the manga/anime series Hellsing)
Then there's Fallout 3 and Fallout: New Vegas, where you can make your character a cannibal and devour corpses in order to heal some of your HP. FO3 had also had a perk, "Hematophage", that enhanced the healing benefits of drinking blood packs; originally, they only healed 1hp but after learning how to drink blood like with the mentality of a vampire, they heal 24hp, as much as a bottle of purified water. Skyrim expanded on cannibalism and has a quest devouted to it.
It's not so much a sexual thing for me: it's closer to spiritual.