Dear Dante,
A demon hiring a demon-slayer is not the joke of the century. A demon hiring a half-demon demon-slayer is the joke of the century.

Also, yes, you have a crotch. We're all aware of this. You don't really need to draw even more attention to it with that gigantic skull...belt-buckle? I really don't know what that thing is, it's only purpose seems to be to draw attention to your package.

Love,
Me

Also, stupid door, why won't you let me through? I have a demon with 25 strength (31, even). Is this not good enough for you? Do you really hate me that much?

And spoiler-filled thoughts on Hijiri.

After a little bit of investigation, I think Hijiri is Cain. I wasn't familiar with any stories about Cain being forced to wander the earth, but I was re-watching the explanation the woman in black gives you, and she says he's atoning for his 'mortal sin' - Eden-mess aside, Cain is the first person to commit a 'mortal sin', when he murdered Abel. So I Wiki'd it, and sure enough, some variations on the Cain legend say he was cursed to wander the earth for all eternity. So mystery solved, I think.