Three loud knocks on your cabin door was what woke you on this day, This day was a special day, it was the one that signified the turning of a page on your book of life, it was your birthday. You scampered down the stairs in order to see who was at your home. Foregoing a shirt you swing you door open to meet half the gaze of the local post-mare.

"Good morning Anon!!!, Happy Birthday!"

The mailmare reaches for a hug, and due to your shortend stature, you are crushed between the light gray bosom of the mare. While desperatly gasping for breath you feel something not quite mare-like press against your front. You see, when you entered this colourful world of technicolour creatures you were very quick to find that mares were gifted with both sets of genitalia, however that is a story for another time.
You realise that you have been released from the hold of the grey mare when she fishes out a blue envelope with a rainbow pattern emblazoned on its back.

"This is for you, I think its from Rainbow Dash"

Derpy's smile meets your deadpan look. You try to be patient with the mare but she makes it hard sometimes. You reply your thanks and close the door as she flies off. Ripping open the letter you find a handwritten note.

'Hey stud. I'll be over with your present when I finish work, Don't eat dinner I'll have something for you'
-Dash

You blush, knowing what Rainbow means with her note. Rainbow was a very athletic mare and had the attitude to go with it, confident and outgoing her first reaction to meeting you was to ask you back to her house for some funtimes. Her being 8ft tall left her endowments literally in your face, it didn't take long to accept her offer. That night you had learned about how pony magic worked, it allowed large objects to enter not so large places and it gave feelings that you were very excited to feel again. With what lay ahead planned, you decide to get everything ready.

It was mid afternoon when Rainbow entered your house, Having given her a set of keys when you got the place you basically gave her right to enter as she pleases. She finds you sitting on your lounge reading a book.

"Hey Anon, I've got your present"

Rainbow reaches into her pant pocket and retrieves a blindfold.

"But you have to put this on the get it"

She hands you the fabric and you eagerly tie it around your head so your vision is removed. You hear the untying of a belt and a thump of heavy material falling to the floor. You hear some more fiddling happening in front of you and start to smell what is undoubtedly Rainbows stallionhood.

Rainbow reaches down to unwrap your eyes. If you weren't aroused already the sight in front of you makes sure you are. There stands Rainbow smirking at you, holding her cock aloft due to its size. You glance at her balls, each the size of a small melon, hanging low in its sack closer to her knees than her body. Your eyes travel along her length and finally rest at the tip where clear liquid is forming. Tied around it is a bright red ribbon.

"Care to unwrap your gift?"

Your reaction was that of a starving man to food. Your hands grab and grasp at anything they can reach, one hand caressing her balls, the other squeezing around her sheath. While your hands are busy you take the head of the massive pole into your mouth and start suckling. You feel a hand at the back of your head, not pushing but rather guiding you onto her shaft. You other hand joins the one at her sheath to start pumping the length not in your mouth.
Rainbows' hand leaves you for a moment and you look up. she pulls at the ribbon currently being drooled on. Is she trying to remove it? You are mistaken as she loosens it enough to slide it further down her cock. Now nestled nest to her medial ring she speaks up.

"if you can make it that far, you will get a very, very special reward"

You look at how far she placed your target and your eyes cross, she must be asking you to swallow at least 20 inches of hard horsecock. Not one to run down a challenge you resume your duty, pushing down starting to break down the resistance to your throat. You would push down every few seconds until you felt a gag forming, then you would retract and continue sucking around the senstitve head.

Your ministrations weren't being unappreciated, by the evidence of Rainbow's moans. You tested the waters of your throat once more and felt the muscle give way to the intruder. Swallowing several inches you begin to feel pressure in your neck. Your hands leave Rainbows length to feel at your throat. you can feel the blood pulse through the bulge in your throat as well as the thick head expand and retract with each pulse. You pull back to gain some breath and when your lungs recover, push yourself down again, spearing yourself on Rainbow.

Hands still on your own neck you squeeze and rub at her length through your skin and are rewarded with rainbows cockhead flaring out and... no climax? You look down at her length to see the ribbon tied around the medial ring is stopping your treat from coming out. Reaching your hands to untie the fabric is met with Rainbow slapping them away.

"Like I said, Reward if you can make it."

More determined than ever you resurface for air and skewer your throat down the cock in front of you, this causes you to gag, throat rippling around Rainbows length. This causes a breathless moan from the mare, it seems shes already on edge from her failed orgasm previously. You continue through your gag reflex for a few more minutes, each time finding yourself stretched deeper over her cock, reaching halfway toward that red loop of cloth.

Rainbow hits the wall once more as her body spasms and cock flares out once more. This time you notice it, out the corner of your eye her once overly large balls are increasing in size! They each have to be as big as your head now. It seems her failed climaxes are giving her literal blue balls. With every throb sent through her junk those balls swell even more until finally at the size of large watermelons they stop.

Cock still lodged deeply you look up and see Rainbows face screwed in concentration. She very clearly wants to cum but is holding herself back for you. You reach out for her arms and guide them to the back of your head and in the moment of realisation or what you mean thanks you. The moment is lost on you hwever as those atheletic arms prove stronger that your narrow throat. What feels to be at least a foot of hard cockflesh enteres your throat. Without even being given time to gag your head is thrown back, and then your vision is filled with a blue stomach as her poweful hips start to fuck your face.
Her thrust continue getting deeper until her balls smack into your upper chest and the makeshift cockring enters your mouth. With every thrust popping her ring into and out of your lips you imagine it wont be long for her. With that knowledge you prepare yourself to be blasted with her cum. No amount of preparing could stop your eyes bulging as with one final push her hips meet your chin, sheath and all snug inside you, thick medial ring pushing against your throat.

"Here's your treat"

Face flush against her groin and with 2 feet of cock inside you, you feel the thick blasts of cum fill you. You feel it settle quickly in your stomach and begin to bloat it with her seed. the stream begins to taper as she pulls back, only to jam her crotch to your face once more, the action reigniting the jets of cum. Eventually though even that cannot keep her climax going and she loosens her grip on your head. You slide off her softening length in order to breathe once more. With steady gulps of air you gradually bring yourself back to normal breathing only to hear the snores of the mare sleeping next to you. You manoeuvre your bloated belly in order to lay next to her, already thinking about you next birthday.

Author's Note

Little something for Screwingwith SFM I know how he adores futa-dash and there was a couple of images I saw that inspired me