Naked Snake: cannibalism.
It's a practical matter--why would he eat from a bagful of rotten things when there's a nice fresh soldier right there still warm and everything? I quite like the idea that it's actually no big deal for him and that he's nonchalant about it.

Would prefer that it be more sensual than sexual, but it is wholly up to you--feel free to introduce a dominance or necrophilia angle if that moves you.