You sneak in and investigate.

Heather goes over to Simon's house, and you stealthily follow her. She goes inside, and you see a few friends of hers and Ms. K waiting for her before the door close. You sneak around the back of the house, and carefully spy them all going upstairs. You wait and confirm that the rest of the rooms are empty of people before you enter through the backyard.

But you only manage to make halfway to the staircase before suddenly Ms. K grabs you from behind!
"Hey, I'm glad I caught you, I've been meaning to talk to you."
"Oh?" Like a little kid on his first date, the nervousness washes over you at her mere sight, let alone her wanting to talk to you. You try to think about Heather. The black MILF takes you over to the living room and sits you down on the sofa. On the table in front of you is a laptop.

"Heather and I have been talking recently," she looks around the room and then catches your eyes, "well there's no easy way to say this. I like Heather, a lot. I think she's a great woman and I think she deserves the world."
"Of course, so do I."
"That's the thing," she smiles at you and you can see the pity (...and glee?) behind it, "you really can't give her what she needs."
"Excuse me?"
"John, I've been with a lot of men in my time and I have to tell you, you always acted like you were small."
You can't push her away. Just seeing her this close, touching you, was driving you crazy, you don't dare to push.
"Men with small ones tend to act differently. I can usually tell within a few minutes. And with you, all those months we worked together, it only confirmed what I already knew, that you were under-endowed."
She moves her hand over your chest and to your belt. Her fingers somehow manage to grasp your zipper without actually touching anything else, and she slowly tugs it down.
"We'll watch the show while I explain..." With her other hand, Ms. K clicks onto a program displaying a camera feed of a bedroom...and the door to that bedroom opens, and in come Simon and Heather!!

On the camera feed, they sit down on the bed before starting to kiss passionately for several minutes. Heather kisses Simon softly on the cheek and whispers something into his ear. The feed has sound, but she said it too softly to hear properly. You can tell it could only have been one thing, she is asking him to fuck her.
Simon stands up and pulls down his pants and boxer shorts. His long thick penis is still soft and it hangs halfway down his leg.
“Oh my god!” Heather exclaims. Her eyes are bulging and her mouth is wide open in surprise.

She kneels before him and places her small hand on it. She kisses it right on the tip and looks up at him with a look of pure lust and awe.
“You have the biggest, most beautiful penis I have ever seen.”
Simon smiles cockily.
His cock is hardening and it expands to at least 10 inches and is still getting bigger, forming a straight 90 degree angle from his waist. Heather continues to watch in amazement as it reaches higher and longer measurements. Arching upward and reaching an impressive level of hardness for such a big organ.
“Oh, your balls are so big!!” She exclaims, reaching instinctively to cup his massive, almost tennis ball sized balls.
She starts kissing his balls and along his shaft in a furry of passion. She goes on, rapidly kissing all around his massive organ for a good minute.
Finally, she stops and looks up at him with a look she has never in her life given you. It was a look of pure lust.
“I need it in me.” She mutters calmly.
“You want it?” Simon says arrogantly.
“Right now!” She pleads. She starts rapidly undressing, almost tripping as she pulls her jeans off as fast as she possibly can.

"I can't believe this..." You whisper in shock.
Ms. K sniggers so loudly that you worry that someone else might hear. She is still chuckling as she begins to talk, her hand still buried in your pants. "See?! You act the small man all the time. Simon is a real man. A very big man that knows what he wants and gets it. I can't say no to him, and I don't want to. Seeing him take control and act like the stud I know he is turns me on. Turns any woman on. That's why Heather there can't take her eyes off him. That's also why he'll be fine giving it to her. A little man like you? You wouldn't even be able to get hard. Now," her thumb pulls away the waist of your tight underwear and slips in, "where is this tiny guy hiding?"
"No," You futilely protest.
"See, one more reason you're just a small dicked little man. I'm telling you Heather is going to be with someone else, and just because my hand is wrapped around your pathetic pee pee, you don't fight back. How can I not give her what she wants?"
She runs her other hand around your front and pushes your pants to the floor. Then she pulls your underwear down too. You're totally exposed, but you don't move.
"This is too funny. See what I mean, what man would let a woman do this to him?"
She leans back and, for the first time, gets a full look at your penis.
"All those years and I was wrong. It is SO much smaller than I ever thought."
Ms. K bends over and smiles at your rock hard, small member. She takes it between her thumb and forefinger, and begins to stroke it.
"You know what's so cute about the little ones? They stand up straight. A real dick stands out and proud, but these little ones poke up." She strokes a little faster and giggles.
She kneels down in front of you. Her intense two finger job is, in every way, perfect - rubbing and stroking and pulling you with just two dainty fingers to the point of explosion. You are already about to come.
She breathes hot air and it mingles with the precum on your cock. Your cock twitches as it gets ready.

Meanwhile, in the bedroom on the feed, Heather is ready.
Her large breasts are still contained within a white bra, she didn't even care about them because she was in such a hurry to get her panties off.
From your secret vantage point, you see that her trimmed pussy is quite wet as she positions herself in front of Simon on the bed and thrusts her waist right against his aching hard-on.
Heather is whispering into his ear, begging him to fuck her with his big dick.
“Do you want a deep dicking?” He asks.
“Please give it to me. Give me a deep dicking!”
Simon positions his tool at the front of her vagina, and she slowly lowers herself onto him.
“OWWWWWWW” she moans as she slides about 4 inches onto it.
“Oh that SO GOOD. SO BIG!” she moans.
"AH! AH" Heather moans as Simon does the nasty with her on the bed.

Heather moans and moans as Simon continues to plow your girlfriend. They fuck for thirty minutes while Ms. K continues to wank your cockette. You've never been so turned on in your life, despite your humiliation. Your girlfriend is receiving **** pleasure and you are powerless to stop it.
"Say it, say you've got a little boy's dick. Say it, and I'll blow you." Ms. K smugly purrs.
"Ahhh," she picks up her pace.
"It's a little boys dick, I have a little boys dick, please please blow me." You whimper, trying to get her to hurry up before you finish.
"Ha! This is even better than I thought. I'm offering you, a pathetic little nub like you, a masterful BJ and you can't even hold it in long enough for me to start, can you? Can you little boy...?" She jerks faster and you are in trouble. "You want to see a big prick fuck your girlfriend? Do you? You want to see her take a real dick?"
"God yes!" You would say anything at this point, anything to get her to not stop.
"Good boy! Good boy. You're going to let her have him to her hearts content aren't you? You're going to let her do whatever she wants right?"
"Right, right." You wince, you're almost done.
"And why is that? Why is that little boy?"
She pinches, and the cum charges up your shaft and towards the head.
"Because he's a real man and she deserves a real man!"
Ms. K doubles her speed, and you start shooting as hard as your small cock can. She tips her head back and laughs as you spurt, only twice this time. She cups her left hand and milks you with her right, pulling out one more half squirt. The watery mix barely filled her hands.
"My god you even cum like an infant!" she examined her hand and its contents. "Your poor girlfriend!"

And speaking of Heather, she is getting implied upon that huge dick.
“I want you to empty these big nuts into me.” Heather yells at the top of her voice.
“You want me to fill you up?” Simon asks again, already knowing the answer.
“I want you big dick sperm!” she yells in response. “Cum in me you big dick bastard, I need your stud cum!”
This time, she moans as he slowly inserts all 12 hard inches deep into her, until she is pressing all the way up against his balls. The stud's pace slows and his rhythm gets shorter into a familiar male orgasm pulse. Heather starts cumming and screaming again as Simon fills her with his load.
“Oh my god! OH MY GOD! OH My.... goooooood!” she keeps saying, as she cums for almost 30 seconds.
When she finally starts to calm down, Simon pulls his still fully erect cock out of her and presents it to her face. Heather kneels down again and repeats the rapid kisses that she had done earlier. All the while, kissing his cock head, his balls and along the length of his shaft, Heather's pussy remains wet.

Ms. K closes the camera feed and the laptop. Turning to you with a big grin on her face, she offers you a chance to even the odds - but promises the consequences for losing her game will be dire.