This started dark, but ended sweet.

Maybe keeping the all powerful monster away from the one person he loves, the one person who can bring him back from the brink of destroying everything, is a really bad idea?

These part ones are too short.

Grandma is a horny old bird.

Oh yay! Here comes the—I mean, oh no! Here comes the rape!

So Haru is the demon, huh?

So Karen is an orphan.

There are so many of them. If Grandma drains all of them, is she draining more from the original or less?

Did he just obtain a harem of willing humans?

Needlessly overprotective dad enters the scene.

Yes, reeducate him. Reeducate him all night long.

They are going to have some explaining to do with Onee-chan being there.

Soon they will all be hobgoblins.

Calm down, Karen, he is not a lolicon. He likes his ladies MUCH older.

Random Amish guy passing by: "AN-I-MALS!"

Oh, shit, she got ate.

Bodily fluid manipulation? Whose? His, or his opponents'? Manipulation of your opponents' bodily fluids would be awesome. Causing them to pee, poop, puke, bleed and cum all at once would be hilarious and overpowered.

I am full from all this cheesecake.

I am sure Haru is not longer horny after that last panel.

I doubt Talk-no-jitsu will work here.