Hi, it's my first story and I hope you'll like it. Apology for any gramatic errors.

Monster Gift: Chapter 1
Birthday Behemoth

Story contains:

Lemons (F/M)
Large Muscle Growth
Height Grow
Body modification
Stomach Bulge
Unrealistic Human Biology

Don't like don't read ^w^

It was 11 PM. A girl named Luna was wandering through park in her city. She was a 21 years old, 5,57 ft (around 170 centimeters) tall beauty of a girl. She had a nice slim figure, lovely round and gorgeous butt and cute small B size breasts that had perfect shape. She had the most beautiful face with bright blue face and long white hair which looked wonderful with her pale skin. Not too pale but the good tone. It was her boyfriend's birthday tomorrow and she still didn't have a proper gift for him. She only bought a bunny suit like the one from Playboy Magazine for herself because she knew he likes them. Hell, he told her multiple times that he'd love to see Luna in one.
"We talk about so much stuff" she told to herself and chuckled slightly.
She also bought him a gift card for their favorite video game they loved to play together but she wasn't sure if it's enough.
While she was walking through the beautiful trees in almost full dark she looked at the lovely sky full of stars. Luna saw that one of them is moving slowly. It was shining in a bright blue light. It was moving faster and faster untill she realised that it was a shooting star. It looked so wonderful, so beautiful. But it kept coming and Luna noticed that it was falling right at her. She got scared and started to run. She didn't want to die before her lover could see her in the suit she so wanted him to see!
After around 10 minutes of intense running she finally stopped and supported herself against a tree. She tought to herself that she has good condition but it could be better.
Luna looked at the sky and saw the shooting star falling closer and closer the ground. Eventually it hit the ground. She didn't hear any loud noise but saw bright blue flash around 300 meters away from her. She stood there for a while and then decided to investigate.
As she reached the place she found the falling object in a small water pond. It was shining so beautifully! Emanating in a splendid bright blue light. After a short while of thinking, she reached for it and grabbed this 'huge' shooting star she was so afraid off burned down while falling and was now the size of a small stone. It was still shining though not as much. She tought to herself that her lover will be very happy when he'll be given a shooting star from her precious girl. Luna blushed as she tought about it.

-Around 1 hour later-

Luna entered their apartment.
She put her white hoddie on the hook and put off her shoes. She was wearing a black shirt revealing her shoulders and bright blue jeans shorts.
Luna went to the kitchen where she put the bunny suit and gift card. She proceeded to put the shooting star in a glass filled with water and watched in awe as it shined.
"Finally home, Loony" Luna heard from behind her back. It was Lux, her boyfriend. He loved to call her that. She turned around with a lovely, pure and innocent smile that Lux loved seeing.
Lux was slightly taller than her, at 5,7 ft (175 cms). He too had naturally white hair which were rare in the year 2034. He was also 7 months older and also had blue eyes though not as bright as Luna's. Luna loved his look but she loved his character even more. He was funny and caring. Loved to have a good time and play with Luna. She tought this he was slightly immature but in a good way. In fact she was thinking the same about herself. She was just like him.
Luna blushed and approached Lux slowly and then hugged him as they always do. They loved each other so much. They first met when they were still kids and it was a love from the first sight.
"So warm" Luna murmured silently,
"So soft" to which Lux repplied happily.
After a while of embracing each other, Luna moved her head off his shoulder and looked at him, blushing slightly.
"Happy birtday" She whispered and kissed him deeply. Every time their lips met, she was the happiest girl on Earth. And probably in the whole world.
"I've got you something. Go to living room and wait there for me with your eyes closed."
Lux smiled and nodded then did what his lover told him to. He went to the living room and sat on their bed.
After about 5 minutes, Lux heard Luna saying:
"You can open your eyes"
And when he did, he saw Luna standing in front of him wearing a bunny suit. Lovely long legs covered in dark transparent thighs, one hidden behind the other one. Higher up, there was Luna's lovely torso in a black suit, revealing her shoulders, her arms crossed behind her back. Then there was her head. She put a black choker on her neck and was wearing lovely black bunny ears. She was blushing in such a cute way.
"I-I-I tought you'd like to see me like this..." Luna murmured, blushing even more.
"And I do, Loony, you look so cute"
"You're silly" Luna said with a slight chuckle.
They embraced each other again. After about 10 minutes of hugging and kissing Luna reminded herself of the rest of his gift.
"There's something for you in the kitchen." She said softly. "Have a look at it."
Lux complied and gave her a headpat then slowly stood up and walked over to kitchen. Luna loved getting headpats from him.
Lux entered the kitchen and looked around. He noticed something laying on the table. He approached it. It was a gift card. He looked at it and tought to himself
"100,000 in-game money. I'm rich!" He smiled and then looked at a glass filled with black liquid that was standing next to it.
-The glass that earlier had a remaining part of a shooting star inside it-
He tought that his darling bought some expensive alcohol for him and took a sip.
It tasted so good. So sweet and warm. Lux emptied the glass and drank all of this amazing black drink. He returned to Luna in the living room. She was laying on their bed holding her right leg upward. She must've been adoring her lovely legs, Lux tought to himself.
Luna looked at him with a smile
"You'll buy the weapon stash that you wanted" she said
"No. We'll buy the weapon stash that we wanted" he replied with a smile
"Also, this drink you've got me. It was tasty as hell. Never drank anything as good!"
"Drink? What drink?"
"The one you put next to the gift card."
Luna realised that it was where she put the glass with the fragment of shooting star.
"I didn't buy you any drink, Lux..."
"No? Then what was it...?" Lux said and felt something weird.
Suddenly his heart was pierced by a sharp pain. It felt like he was stabbed by a sword that was at least 1000 degrees hot. As suddenly as pain appeared, it left him. Lux felt a warm sensation filling his heart, then chest and eventually rest of his body. It was like nothing he ever felt. It was warm and nice, very pleasurable.
"Lux...?" Luna said softly, visibly worried about her lover.
Suddenly, Lux felt the pain returning but this time, it was all over his body and not as sharp.
Lux looked down and saw that floor was slightly further down than usual.
He was growing. Fast.
His whole body becoming larger, his limbs longer. His torso and head were growing aswell, keeping his body in good proportions. He was growing taller and taller. Luna stared at him in shock.
Suddenly, Lux started to feel something else. Pleasure. It was growing more powerful every second, he quickly forgot about the pain. He felt the pleasure filling his entire body. It was oddly erotic. He felt his muscles twiching all over his body. His body filling with more muscles and mass. His clothes were becoming tighter and tighter, his skin pressing hard against it and stretching itself so taut.
His muscles were outlining his clothes. He and Luna could see the outline of biceps growing inside his shirt. His arms getting more and more muscular. Eventually his shirt gave up, ripping and tearing to shreds. His biceps were looking like there was a basketball in each. His arms were much thicker than they were before. Weird thing is, there were no vains visible on his smooth skin. His pecs were massive. They were standing few inches away from his chest with widened greatly. His waist widened a lot aswell. He was happy that he wasn't looking like these freaks with tiny waists under massive chests. Then he saw his massive abs and his astonishing 6 pack.
His massive calves stretching his pants wide and his thighs doing the same even more.
But he kept on growing. Rapidly. He was also still getting taller.
*Riiiiiiiiiip* and his pants ended up ripping to shreds just like his shirt did. He was now standing only in his boxer shorts.
There was a large bulge inside them, Luna looked at it with mixed feelings. She could only imagine what was inside.
Lux kept growing, his skin and body so taut and his muscles so full. He felt like the balloon seconds before it pops, but he never popped. And unlike balloons, he wasn't filled with air. He was filled with muscles, mass.
He kept on growing and growing. He felt intense pleasure and pressure building inside his manhood.
It was growing aswell. Rapidly.
*RIIIIIIIP*
His boxer shorts gave up. It was inevitable. They simply couldn't maintain such member.
And what a member it was.
Long, thick. And oozing with pre.
After what felt like eternity for Lux, the weird feelings left him and he stopped growing. He was big. No not big, huge. No, he was monstrous.
He was now 11,5 feet (around 3,5 meters) tall.
His arms were at least 5 times thicker than before. His biceps were three or four times the size of a basketball. His pecs massive, far larger than pillows that Luna was laying on. His chest must've been 1,5 meters (almost 5 ft) wide, or even more! His calves were massive, twice or triple the size of a basketball. And his thighs, slightly larger than his biceps. He had a stunning iron 10 pack filled with massive abs. His waist was massive too. He had a thick neck and large, proportional head. Lux looked down and saw a beautiful monstrocity that was now his cock.
It was 2,6 ft (80 cms) long and 25 cms (0,8 ft) in diameter. Fully erect. Then, there were his massive balls, the size of basketball.
It was monstrous. -He- was monstrous.
Luna stared at Lux. She wasn't sure what she was feeling. Shock? Fear? Awe? Probably all of it.
"L-Lux...?" She said slowly and silently.
"Luna, I feel...Great" He answered. "In fact, I feel better than ever. Just look at me!" He started flexing his massive muscles. "Whatever that drink was, it was the best gift I could've ever got! Thank you so much, Luna!" Lux looked at his beautiful girl, laying there, she looked so tiny, so fragile. He felt an urge. An urge too strong to be denied.
He looked her straight in the eyes and smiled devilishly. His cock throbbed.
He slowly approached Luna who was laying on the bed. She crawled backwards a little.
"I'm happy that you're feeling good but...Shouldn't you put something on?" She said blushing.
"There's nothing that would fit. Besides...Clothes would only disturb us now.
He put his hands on the bed on each side of Luna and leaned over her.
"B...But Lux...-"
"No buts, Luna" He interrupted and carresed her face. "I don't want to ruin this lovely suit. Please, take it off" He said in such a manner she couldn't refuse. And even if she tried to, there was no chance. He was twice the size of her!
Luna quickly undressed. Again, she was laying on their bed while Lux was standing tall over her.
Lux grabbed her thigs. His hands were big enough to cover entirety of her thigh. He spread them apart with brute force. He was so strong.
"I don't think I can-" Luna said but was interrupted by Lux. "Then don't think. Don't worry, Luna." He moved his face towards her beautiful, shaven womanhood. Lux moved his mouth closer and looked Luna in the eyes which she answered to looking into his.
He opened his mouth and let out his massive tongue. It was as wide as Luna's 10 fingers. He licked her lower lips and Luna let out a loud moan.
Lux rubbed her clit with his tongue, making circles around it. It sent shivers down Luna's spine. She grabbed into the bed sheets to have anything to hold.
Lux was licking her pussy now. He was doing it slow firstly but then sped up to much faster pace. Luna was moaning at this stimulation. Her nipples became erected and she started to grope her petite, perfectly shaped breasts.
After few minutes, Luna felt pressure down her body. Lux was pressing his massive tongue against her vagina's lip.
"Lu-" she tried to speak but was interrupted by a loud pop as Lux successfully pushed his tongue inside his lover's love hole. She groaned loud, being spread so wide by Lux's wide tongue.
He pushed his tongue deeper and deeper inside his girl. She was moaning loudly. Not only from pleasure but from pain too. The pain was stronger than pleasure and Luna started to sob tears.
Lux didn't want to hurt his girlfriend so he moved his tongue back a little. He started to swing his tongue around inside Luna's cunt, licking her inner walls to comfort her.
It seems it worked. Luna blushed.
Lux started to push his tongue deeper again while still licking her insides. Pain started to fade away slowly as Luna was becoming more and more aroused by her monster lover.
"Lux..." Luna moaned and began to stroke his head as he was penetrating her with his tongue.
"Your...tongue is longer than-AH!" She growled as Lux pushed his full length down her hole. He knew what she wanted to say and he knew it was true. His tongue was now 15 inches (38 cms) long.
With such brute force that Lux now possessed, he quickly pushed through her now wide cervix and into her womb. He was licking it from the inside.
It felt amazing for both of them. Luna tasted so good for Lux. And Luna was loving having her womb licked from the inside. His tongue was all over her inside. That was enough to push her over the edge. A powerful orgasm ripped through her body. She never felt anything like this before, she hadn't even imagined something like this was possible. Luna moaned and whimpered. Lux noticed that and didn't stop licking her insides. Instead, he became even more aggresive. He kept licking Luna's womb, his tongue twiching, squirming inside her, elongating her orgasm. After 5 minutes of constant orgasm, Luna was so tired. It was becoming too much for her to continue.
"L-Lux..." She moaned "Please...You can...stop now...It's too much for me..."
Lux turned his eyes from her pussy and looked at her with a devious intent in his beautiful eyes.
He kept licking her womb but he started to push his tongue up, higher and higher.
"Ah...N...Noo..." Luna whimpered. Lux kept going and eventually Luna saw a small bulge on her belly, right under her navel. It was Lux's tongue, distending her stomach.
"Hurts...Hurts..." Luna was whimpering "Please, L-Lux...Stop it"
It did indeed hurt but that wasn't the main issue. The pleasure was so intense and Luna was so tired. She couldn't keep going like this. But she loved the pleasure that her behemoth boyfriend was giving her. She ceased to protest and began moaning even louder. She reached her orgasm again. She screamed "LUX!" and came all over Lux's face. Her head fell down but he kept going. She slightly raised her head and looked at Lux. *He must be smiling" she tought.
Suddenly, she felt movement in her womb ceasing. Lux's tongue backed off but remained in her cunt. Still twirling, like it was seeking something. It blasted itself into her womb again, extremely tongue was carressing her womb. And then she felt it: His tongue reached her fallopian tube. "No! Please, don't!" Luna protested. She knew that it couldn't stop Lux. Actually, the fact that she was so defenseless and at the mercy of her beast of a lover was making her even hornier.
He plunged his tongue into her tube. It was so painful. That part of Luna's body wasn't made for this purpose yet she started to feel so good. Lux started tongue-fucking it. Faster and faster. Luna was smashed with a powerful orgasm again as she was moaning. Lux wasn't satisfied though. He pushed his tongue all the way into her ovary. He filled all of it with his massive tongue. Luna orgasmed again, immedietaly. She realised how tiny her vagina was. How tiny herself she was.
Lux was twiching his tongue inside and pulled back, then did the same with the second tube and second ovary.
After Luna orgasmed two more times, she moved back to her womb, where he kept tongue-fucking her and licking the back of her womb at the same time. After Luna's 20th orgasm ended. Lux slowly withdrew his tongue from his girl. It made a wet "pop" as it left her twiching, slightly gaped pussy.
Luna was laying flat on her back, arms limp from all the pleasure and pain she experienced. She was so exhausted.
"It was a very nice hour of tasting you, Loony. Did you enjoy it?" Lux said with a smirk while he still held her legs wide.
"H...Hour?" Luna murmured weakly "It felt like eternity." She was panting so hard.
"You didn't say no" Lux said and chuckled. "Now it's time for the main point" He said as he stood up, his long, fat monster cock hanging while Lux still held Luna's legs hostage.
Luna stared with horror and anticipation.

-
So that was it for the first chapter. Hope you liked it. I will continue writing this story as I really enjoyed it. Next chapter will contain more sex and ravaging of Luna's body.