You find yourself walking up to Fluttershy's cabin. You make your way to her door and knock.
A friendly face greats you, it's Fluttershy, she says "Hello. How are you?"
You "good, I got your letter, you wanted to see me?
Fluttershy "I was hoping... you don't have to... but... could I try somthing with you?"
You "Anything!" Your mind is racing with dirty thoughts. But you take a breath and calm yourself.
Fluttershy "ok" she blushes and looks slightly away from you "I... want to try... ballbusting"
You think "Uhm No!" But end up saying "Ok why not"
Fluttershy "Really! Ok, thank you! I'm going to try and be assertive!... if that's ok? Follow me to my bedroom."
You do as she says.
Fluttershy "could you please undress?"
You do as your told
Fluttershy "Ok... so I'm going to try and kick them... so spread your legs... Ok?"
After you do, she turns around granting you a great view of her gourgous ass. You stare watching how her long tail sways slightly with the movement of her hips, she looks gorgeous as she looks back at you. Then as if you forgot all about it "BAM!" She bucks you straight in the balls, much harder then you where expecting almost as if a professional boxer just punched them. You notice her quiving sexually as she stairs at your junk swinging from her blow, clearly turning her on. She then starts to look a bit panicked and spins around just as you start to double over.
Fluttershy "OMG! I'm so sorry, I didn't mean to do it that hard! Are you ok? Let me get you some ice" she then looks a little closer at your balls " Are they still attached!? Oh dear! OMG! I'm sorry, I could get ice or I could try somthing elts"
You want to tell her to get ice but your to curious about the other option so you say "just stay with me, thank you"
She already being very close to your crotch, leans in and puts her mouth over your very hard cock that you just now realize is hard. She starts giving you the greatest BJ of your life and you immediatelyforget about the pain. Then you make the mistake of saying "oh Fluttershy it's, mmmmmmm, not that bad"
She slowly stops her magic with a few more teasing flicks of her toung. Then says "Oh! Thank Celestia! I'm sorry, if it makes you feel any better I did enjoy it alot"
You " well if you enjoyed it then we can do more" hoping she would be satisfied with one more kick and you could resume the BJ.
Fluttershy "Oh! Really! Are you sure? I'll be much more gentle, promise!" She playfully pushes you onto the bed, then lays between your legs on her stomach looking at you in the face, with a beautiful smile. She then looks down at your balls and playfully taps them with her front hoof. It feels good and she is clearly enjoying it as well, she continues for a few minutes, then looks up at you and says "Would you mind if I could squeeze them a bit?"
You reply "Anything you want"
She looks at you with big eyes and says "Would you please pass me tgat pile of books beside the bed? Because with my hoofs it would be to hard to squeeze them together"
You hand her the books and she tenderly lifts up your package and slides the books under it. As you prop yourself up on the backboard of the bed.
You heard her wisper to herself under her breath "be assertive"
She then says to you in a sexy but dangerous voice "Hold your cock! If you could..."
You do so.
She then skillfully places the top book cover elastic band over your sack so that the balls say nicely placed on the top book. She then places one hoof above your balls and says "Um... is ten ok?" You nod yes. She takes a deep breath then stomps your balls 10 times with fair force. You can see on her face that its starting to make her wet. She looks at you again with big eyes and says "10 More please!?" You nod yes again. But this time you can really feel each time her hoof comes stomping down as a jolt of pain travels up your stomach. She then positions each of her back legs on either side of your right leg and starts to very happily grind up and down the length of your leg. She says to you in a half worried and half to horny to care voice

"Are they ok, are they still in one piece?"
You "I'm fine"
She squees happily. Then gives you another 10 hard hits to your balls. She notices that its a bit much for you so she starts to give you another BJ but to your surprise she also has your balls in her huge mouth. For a few minutes she is grinding furiously on your leg as she sucks on your balls and cock. Then suddenly she spits out your cock so only your ball are in her mouth and she says holding the balls in her mouth "if this is to much for you, let me know please" then sucks your balls so hard it's almost unbearable, but you can tell she is going to climax soon so you hold your toung. However are she gets closer and closer to climax she sucks harder and harder on your balls so in order to deal with the pain you start stroking your cock desperately, trying to alleviate the pain. Before long you find yourself exploding all over the top of her head and as you do so you feel an insane rush of pain in your balls as she starts cumming uncontrollably and no doubt accidentally bitting your balls with far more pressure then she intended.
She finishes and slowly relealises what's still in her mouth. She releases your orbs and you instinctively grab your throbbing sack. She slowly stops quivering with pleasure and panicked says "OMG! I'm sorry and bolts to the kitchen, she quickly returns with a cloth that has ice wrapped inside. She gently places it on your balls and says "was that ok?"
You quickly reply "That was teriffic" even if your not sure it was. She smiles slightly and gets up on the bed to snuggle up to you. It feels so nice. You both lay there for over a hour, snuggling happily. Eventually you depart knowing that you'll definitely be back.