Well it's more than that, démons feed on humans' essence, it just so happens that to get that essence they do sexual things (because this is a yaoi so ofc)
At first I thought they were talking about the life force or something like that which the seme gets by kissing, but now idk. I'm confused (￣∇￣")
Making out is mr. Demon's way of feeding on mr. Human. He's only making out with him to get a taste of his essence, so it's basically like sucking on a candy or a lollipop. So kind of like eating, which is why they call it that.
Oooo yeah that would be tasty for us...Ya know....essence=cum.
Why are they calling making out "eating"? They're in high school, surely they know what making it is right? Or is this a "lost in translation" kinda thing?