i disagree with kuroe after reading this many, MANY times and reading all of the authors notes as well. I think its more of a mental thing and exerting a different kind of pressure, or desire. different from just arousal and more like a uniquely demonic...trait? not sure how else to describe it. think about how hodaka bites hiyori all the time, but it was only one instance in which he marked him. its more about intention than the action itself. does that make sense?
hence why they can make out and be intimate normally, but when hodaka starts thinking "I want to eat him," the nature of it changes. its the same on hiyoris end, where it can be normal, but when he feels hodakas pressure its like a mental switch is flipped from "making out" to "eating"                                            

		
To this day, i have no idea what “eating” means