Getting BIG (TG, TF) FULL STORY EARLY ;)

Sister's Party Pants (TG, TF) <- this story provides some context, enjoy!

    You were finally going to complete one of your resolutions from New Year's Eve and start hitting the gym. You were getting your bag ready and threw some random work out clothes you found on your floor into your bag. You got your protein shake ready and started driving to the gym ready to get buff. When you finally arrived you heading to a changing room and unpacked your bag, grey tank top, camo pants... had you ever had those... and your sisters sports bra ended up in your bag somehow? That was odd, but you figured it got put in your laundry by mistake. You slid off your jeans and put on the camo pants, they were really nice and soft, and had a familiar feel, but they were pretty tight especially around your crotch. "Wait... these are my sisters pants." you said annoyed. You went to slide them off when they wouldn't move... "OH NO! Not again please." you said freaking out, the last time this happened things got very out of hand. You quickly grabbed your phone and saw a message from your sister, "Can't wait to see how big your ass gets after squatting." she said with a winky emoji. You were fuming, but the feeling was already hitting you like a pile of bricks.
    The pants started to squeeze your legs, but unlike last time they didn't grow and the pants started to feel looser. "Huh, odd." you said to your self. But before you could think about it too much your hair started growing out and was as silky and soft as the last time. This time it styled itself differently into two braided tails that felt so nice against your shoulders... wait when did you put this tank top on?! You breast started growing and expanding, and at the same time your lips puffed out, your eyes turned the same blue as last time, and your face quickly changed into that of your sisters. "Man my ass is looking flat!" you said to yourself and quickly became confused on how that came out of your mouth. Before you could think about it much more your tits reached terminal mass and were shaking up and down. You fondled them for a moment until you realized you were seemingly done transforming. "Why is my butt so small this time?" You wondered. But that thought quickly went away as you felt the sudden urge to start squatting. You sprinted over to a rack, and ironically that made your rack jiggle. You put the weight on your back and got ready to squat. You went down. ONE! You went down again. TWO! And with each count. THREE! Your ass grew. FOUR! And grew. FIVE! And started to jiggle up and down. SIX! Bounce everywhere. SEVEN! And it had finally reached the same size as last time, but you kept going. EIGHT! It was getting unreasonably large. NINE! You had the nicest butt in the whole gym. TEN! You were finally done, and your ass made it feel like the slightest wrong move would make your camo tights explode.
    You went over to the mirror and bounced your new found dumptruck, and were really proud of how it turned out. "No! No! I can't let her mind games get to me again." you said to yourself. But just as you thought that, a hunk of a man appeared behind you in the mirror. You immediately bent over and acting like you were tying your shoe. You made sure to wiggle your butt slightly to give him a lovely sight. He gave over and gave it a squeeze, and picked you up like he was your knight in shining army. You looked up into his dreamy eyes, and started feeling his pecks as he carried you to a dressing room. You tried to fight the feelings but couldn't. He let you down and you both immediately started making out, you kissed each other and he reached down and started fingering you. You started to moan and drip as your body was filled with warmth and you forgot about ever being a man. You slid down his pants and starting sucking his dick like a veteran of dick sucking. You went up and down till he came and gave you the best taste of your life. You swallowed it and came laid down spreading your legs as he pulled off your pants, "well at least there off now." you thought as he started thrusting into you causing you to immediately forget about being a man again. He thrusted in and out and left you feeling incredibly satisfied. After he had finished you both cuddled in the locker room for a few minutes until his watch started beeping, "ah shoot, I gotta head home." he said, "can I get your number?" he asked. "Sorry honey, I only fuck once." you said with a wink and quickly put your clothes on and ran out to your car and left as fast as possible. When you arrived home your sister was blown away at the size of your rear, "man... I gotta hit the gym more, I didn't realize the potential my butt had." she said still staring. "Keep dreaming girl," You said twerking a little, and walking up stairs to your room swaying your hips sexily. "I will never let him live that down." Your sister said after secretly recording you. But hey, who cares, you had the best sex of your life today.