Usually helps to get permission before taking someone's character for your own usage.

Oh so you got permission from Kabao kikkawa to draw Yoko Littner?
And premisson from Ben Bates to draw Sally Acorn?

There's a difference between fan art of a licensed character and fan art of someone's personal original character dude.

Don't get defensive.

Is there really difference?

One's a product, one is someone's imagination.
If nothing else it's just basic good manners and etiquette if you're taking someone's character and hosting it on the same site.

I'd agree with Dragon_Nexus, honestly - at least (and especially) if it comes to erotic/fetish artwork, it's better to ask permission to draw someone's char. Just for examples, Lauren Faust didn't really care much about porn pics of MLP:FIM characters, but when people started to screw around with character she created for herself, and doing so in not-so-pretty ways, she was pretty unsettled and creeped out by that. Same here - if original creator has some kind of personal attachment or relation to the character, it's just not very ethical to use said character for your personal amusement or to satisfy the fetish without permission to do so, because, well, you don't even know how its owner will react to this, what if he gets insulted by it?

I honestly wouldn’t have done this if there weren’t already multiple Bondage fan pics of Beatriz.