You walk down the busy street toward Melanie's gym, and you're not happy about it. You were in the middle of experiment when your sister called you to her gym claiming that it's very important, she not often contacts with so you decided to at least hear her out.
By some reason there was 'closed' sign on the door, but you open the door with keys Melanie gave you earlier. As you enter inside clerk lead you through surprisingly quiet and empty hallways into dark room and suddenly closed door as you enter the room.
"Hey! What the fuck?!" - you exclaimed as you suddenly found yourself in dark closed room, but before your eyes could adjust to the dark the light turned on.
"Surprise!" - exclaimed several voices around you, you recognized some of your colleagues and friends, but seconds later you were engulfed by someone's warm and fat belly. Looking up you immediately recognized this smiling face.
"Happy birthday, sis!" - Melanie beamed as she tightly hugged you, raising you from the ground. Melanie is couple years younger than you, she had same blond hair as you and her skin is slightly lighter. That's where your resemblance ends, while you have average height and some curves, Melanie is really big. She's about 10 feet tall and very fat, her breasts are large, noticeably bigger than your head, they rest on top of her huge round fat gut, it's much bigger than beachball and somehow keeps pretty spherical form even when it's empty(which is rather rare occasion), and a little lower are her very wide hips and large butt, she's so wide that they have to widen all doors in the gym, but Melanie still have to squeeze herself through them.
"A birthday? That's why you called me?" - you asked when she placed you back on ground.
"Yeah. I even gathered your friend here!"
"Uh... Damn, I was in the middle of research."
"Oh, sis come on don't be like that! There's also drinks and snacks, here take it!" - she give you a cup with some drink inside.
"Okay, okay. I won't go away, but you know... I'm not really good with alcohol..."
"Ah, don't worry! I'm here to help you! So, cheers!"
As you drank your drink you felt as your head start spinning, this was much stronger than you thought and combined with your weak alcohol tolerance you were drunk after couple shots. Your vision become blurry and you couldn't remember much later, you received some congratulations, had ate snack and some drinks, tried to convince Melanie to fix her reformation machine, though doubtedly that she was able to understand your drunken mumble, and then you finally blacked out. Later, probably in morning, you woke up with hangover and you're...