Tokyo Ghoul

From Viz:
Shy Ken Kaneki is thrilled to go on a date with the beautiful Rize. But it turns out that she’s only interested in his body – eating it, that is. When a morally questionable rescue transforms him into the first half-human half-Ghoul hybrid, Ken is drawn into the dark and violent world of Ghouls, which exists alongside our own.

Note: The prototype chapter won the Young Jump 113th Grand Prix award in 2010.