Version 1

Yuya was expariment on and became half ghoul so he has to eat people but he refuses to do that, althought he has a cross personality that doesn't care and will eat people.

version 2

This world there's a second species who have to eat human parts or they die, they have been around since humans and now they coexist with them Yuya is one and his job is to  deliver food, both for these ghouls (I'm just call them that) and humans.