(I know I know my detail about this is poor but I don't want to be a spoiler) The poor boy was crushing on some chick and had a little date. Then when she turned out to be a ghoul and try to eat him, a construction accident happened, they got killed, and he had to get an organ transplant from the dead chick. He became half human half ghoul. He haves to eat humans in order to survive because ghouls tastes are different than humans. They can't eat what humans could because to them it tastes like slimy moldy sponges.
OK to shorten it up. He works at a cafe called Anteiku. Where he meets other ghouls who don't want to take a life of a human because they have relationships with one. From then on he accept the fact he's half ghoul and human then, more F up events happened and he changed a lot... (♡_♡) Season 1 and 2 waiting for season 3