Scenario: Mario was just about to face off Bowser Jr after the defeat of the other Koopalings, but something odd was about Junior, he was a Power Bottom exhibitionist, and wants Mario to join in the family. Mario would refuse to, so Junior had a plan to make him, and that was to kiss him, suck him off, ride his penis, etc.
Mario has been going world through world on the search for his girlfriend, Peach, but whichever castle he would go to, he would always run into the Koopalings, who would try to get Mario to join him, but of course, they kept getting beaten by the plumber hero. And one of them is not exactly a Koopaling, but somewhat acting like a young version of Bowser. In fact, he’s the son of King Koopa himself. His name was Bowser Jr. or Junior, for short.
Ever since the incident at Isle Delfino, he was always a thorn in Mario's side, helping his father with his plans and in kidnapping 'Mama Peach', as he calls her. He proved to be quite persistent like his father, always coming back for more, determined as ever. He seemed to be the final member before Bowser himself.
But as time went by, Junior went through...a few changes, except he still had that mischievous evil child energy...with a few touches. Mario doesn’t know it til he gets to the tower where Junior awaits. “Well, it’s about-a-time I show Bowser’s son a piece of my mind!” Mario said, looking up at the tower before entering.
Once Junior was taken care of, it was just him and Bowser and it would just be another day. Unlike some of the others, Junior seemed more crafty than the rest of his siblings and his father. Maybe some experienced helped him throughout the years. Whatever the case... it was time for another showdown with the Koopa Prince.
Like a hero, he kicked the giant door open, ready for battle. “Alright Bowser Jr, time to teach you a lesso- huh?!” Mario’s speech was interrupted as Junior’s small changes were finally revealed to him.
Junior had definitely changed over the years. He was still a brat, that much hasn't changed. But his body... He was surprisingly curvy and looked feminine. He almost has an hourglass figure. "Finally! I thought I was gonna get bored! You took care of my brothers and sister? Ppht. Typical." Junior says and grins at the plumber.
Mario has no words to say after being easily distracted by Junior’s body. Hell, it looked like he was thicker than Peach! but he still had to fight Junior.
"I hope you're ready, Mario! I got some new plans up my sleeves! You're not taking Mama Peach again!" Junior says and laughs, getting into a fighting stance. Nevermind Peach, this Koopa pretty much put most females to shame! How did he get like this? His father's genes? Or his unknown mother? Or maybe genetic? Wait, why was he thinking about this?! He has a Princess to save!
 “New plans? what-a-plans have you got, huh?” Mario said, in a fighting position, charging up a fireball.
The Koopa Prince grins, something seemed off. Sure, he was cocky but this time, he seemed so sure he would win. "Oh, I have a way that'll make you submit to me! And trust me, I'll totally enjoy this!~"
 “I will never submit to you!” Mario threw the charged up fireball at Junior, but it didn’t do anything to Junior. Why didn’t it work?! How is Junior ineffective to fire now?!
"Hahaha! What, expected me to be hurt or fly back? I've been training with my Papa! Your fire tricks don't work on me!" He developed an immunity to it now? This didn't seem good. "My turn now~" Junior jumped into the air and tackled the plumber, it seemed he got faster too, despite his body type.
 “G-Get off of me!” Mario tried everything he could to get Junior off of him, but nothing worked for him. He was in big trouble now!
"I finally have you, Mario! You're all mine, ehehe~" Junior giggles, sitting on top of the helpless hero. The small and thick Koopa leans down to Mario's face and gives a lewd smile. "And I'm gonna do all sorts of kinky shit to you~" He whispers.
 “Mamma Mia...” There was nothing left for the plumber hero to do, but he still never accepted defeat.
And then, Junior leans closer and plants his lips on the Mario's, actually giving him a kiss. "Mmmh~" What was he doing?!
Mario felt like something weird was going on with himself, and with Junior kissing him, his love for Peach faded away a bit, and started making way for Koopa males!
The Koopa pulls away for a moment and giggles. "Oh? Liking when a boy kisses you? Weirdo~ But whatever~" He goes back kissing the other male, squirming on top of him and shaking his plump ass. "Mmh, hmm...~"
Mario’s mind was going crazy, his mind is telling the plumber to fight Junior, but now parts of his mind is telling him to fuck Junior! Mario couldn’t resist Junior, he needs do something real fast or-
Junior pulls away once again, seeing the expression on Mario's face, guessing what he's thinking right now. "You like this, don't ya? I bet you wanna do all sorts of fucked up things to me, huh?~" He teases the plumber, squirming in place again. "Just one kiss and you're hooked? Hehe, you're so lame!"
And Junior was right, after that whole kiss Mario’s been through, his powers were getting weaker, and there was absolutely no way he could use them.
"What do you want me to do. Say it." He ordered Mario, he looked serious about this. "I know you're getting off to this. But I won't continue if you don't spit it out. So say it. What do you want me to do."
 “Give me a blowjob!” Mario shouted, betrayed by what he just said to Junior.
That was all he needed to hear, Junior smirks and gets off for a moments. He was on his knees as he fiddles with Mario's overralls. "Where's the stupid... ah-hah!" Finally, it popped out. Mario's erect and throbbing cock. "Mmm... I'm gonna enjoy this~" The Prince opens his mouth and trails his tongue, tasting the hero's shaft and teasing him. "Hahhh...~"
 “Mamma Mia...” This was all Game Over for Mario, except...he kind of enjoyed this feeling with Junior. Hell, It was a better feeling than with Peach!
Junior continued trailing his tongue up and down, tasting the male's shaft. "Hahh... ahh..."
Mario’s mind was breaking, and now his mind is focusing on fucking Koopa boys now. No longer will he think about saving Peach now, he wants to save a Koopa boy’s heart now~
The Koopa Prince was done tasting his cock, now he wanted it proper. He opens his mouth and takes the head inside. "Mmhfhh~ Mmh..." He slowly bobs his head, and stares at Mario, seeing what he was doing to the so-called hero.
 “A-Aah~!” Mario moaned loud, watching the Koopa Prince sucking off his penis, and is about to accept defeat soon. Damn, Junior was good at this~!
Junior turned his focus back to sucking the plumber's cock, swirling his tongue and moaning. "Mmh, slurp, mmhg, mmgh, nh...~" The Koopa Prince may have had a little practice with some secret toys he has, but actually tasting a real dick? He wondered why he never did this before. Junior closes his eyes and bobs his head at a normal pace, hearing Mario's moans of pleasure.
When Mario was with Peach, she and the plumber never had any real sex before, but now someone else is doing it with him, but it’s a male, and it’s a Koopa? He wondered why he never experienced that before.
The Koopa was enjoying the taste of the male's cock, swirling his tongue some more. He wondered... could he go deeper? Junior inched himself slowly, feeling the dick touching the back of his throat, making him gurgle and choke a little. He'll probably never experience this again, so he makes the most of this moment. "Ghgh... ghhhn..."
Mario moaned even louder, but felt a little poke from Junior’s fangs, but it only hurt a little bit, not damaging his penis or anything. Mario felt like he was going to blow his load right away!
Junior breathed through his nose, tasting more of Mario's cock and tasting some pre leaking out. Oh God, it was gonna happen~ Down below his crotch, his cock and balls were revealed and his dick twitched in pleasure. He was eager to taste his first ever load~ He opened his eyes halfway, almost begging to taste it. "Hhgh... ghhhh~"
 “J-Junior! I’m gonna~!” And after saying that, Mario blew his load into the Koopa Prince’s mouth, filling up his mouth til he could gulp it down.
"GHHHGH!!!" Junior's eyes roll back, tasting that warm and delicious cum pouring down his throat and into his stomach. He gurgles, struggling to taste it, some even leaked out of his nose. "Nnhg... ghgh... bhhghg..." Oh fuck, this was amazing!~ Why the shit didn't he do this before?! Forget his toys, this was MUCH better!~
 “Mamma Mia...~” Mario felt like in heaven right now after blowing that HUGE load in Junior’s mouth.~
The Koopa Prince pulls away and gasps. He could still taste the plumber's semen in his mouth. He gulps the last of his load and sighs. "Hahh... f-fuck... s-so much... Mmm~ I should do this more often~" He says and smiles, and still sees Mario hard. "Mmhh... I bet you want something other than my mouth, huh, big boy~"
 “Y-Yes I do...I want your....your....booty~!” Mario shouted again, this time, not betrayed at all. It looks like Junior’s about ready to act more like a power bottom and ride the plumber’s penis~
Junior stands up and walks over to Mario, his plump ass towering over his erect cock, covered in leftover cum and saliva as makeshift lube. "Mmhh... I can't wait to have a real dick inside of me~" He lowers himself, feeling the tip. "Mmhh..." Finally, it slid inside, making the Koopa groan. "Nnh... fuuuuck...~ It's in~"
Mario had the same feeling too, of having a real ass on his dick. “Mamma Mia...~”
The young Koopa femboy started moving his hips, riding Mario and moaning softly. "Hhahh... ahh... H-how's my ass...? Better than a... ah.. ahh... w-woman's right? Oh, God...~" This felt so good~ This felt so damn good~ He was a fucking moron for never doing this! Fuck his toys and Koopa girls, THIS is what he needed~
 “Hhaaaah...It’s WAY better than a woman’s~!” It seems like he just accepted defeat already, he’s no longer a female lover anymore, he’s a Koopa boy lover now, and now his mind is completely broken, with Koopa asses jiggling around his mind, especially Junior’s~
Junior smiles at that, and decides he's done playing around. He was needy, he was horny, and he needed a good fucking~ "Good answer!~ 'Cause we're just starting!~" He starts speeding himself up, riding and slamming his fat ass on Mario's cock. "Aaahn!~ Hhnh!~ Fuck yeah!~ Breed me, bitch!~"
 “Aaaahn~! F-Fuuuck~!” Mario moaned completely loud, hearing Junior’s dirty talking and watching his fat ass bouncing up and down on the plumber’s cock~
Junior brought his arms behind his head and couldn't stop himself from moaning and panting like a slut. His cock rock hard and leaking pre as he rode Mario's dick. "Aah!~ Hhah!~ Yeah!~ Fuck my femboy ass, Mario!~ This is all you need! This is all I need!~ Mmhhf!~" He didn't care if he sounded like a complete whore, why would he care at the moment? Besides, it was just them.
 “Aaah~! Hhaaaah~! You’re the best, Junior! I’m proud to be a part of the Koopa family~! Aaahn~!” Mario felt like Mushroom Kingdom didn’t need him, the Koopa Tribe needed him, badly~
The Koopa Prince blushes, and his eyes rolled back. "Hah...!~ I-if you wanna be in the family... Then fucking take me!~ Don't make me do all of the work!~" Yes, this couldn't have worked out better if he tried. His Papa and siblings would be so proud~
Mario then grabbed Junior hips, and slammed his butt down his penis, going up and down, now making Junior more submissive than ever!~
Junior gasps, hearts slowly gathering in his eyes. "Aahn!~ Yes!~ Fuck me!~ Please, Mario!~" He starts moaning loudly, panting like he was in heat. All thoughts of his pride was thrown out the window. He NEEDED this. So badly~ "Claim me...!~ I'll do anything!~"
 “I’m gonna cum again, do you want my cum, Junior? Do you want it?~” Mario said, acting more powerful than he was.
The Koopa nods his head quickly, his cock twitching and just aching for release. He wanted it so bad!~ "Yes!~ Cum inside me!~ Please!~ Don't make me beg!~" He whined, but he could stop himself from smiling.
 “Then...here you go!!!~” Mario then came loads of buckets inside Junior’s warm ass, filling his belly up, making it look like he was pregnant.
Junior screams in pleasure, feeling himself getting filled up. "YES!!!~ Oh God, yes!~ Fucking cum in me!~ I'll be your Koopa Slut whenever you want!~ Aaaahh!!~" He didn't care that he lowered himself like this. This felt so amazing!~ "Hahh... M-Ma... Mario...~ Aaaahh..." The hearts appeared in his eyes, his mind was all over the place. But he was so happy~
 “Haaahh...Junior...~ You’ll forever be my Koopa slut...~ I’m pretty sure your siblings are gonna enjoy me being part of the family and fucking their Femboy booties like how I did with yours~”
Tears ran down Junior's face, as he giggled, feeling the warm cum inside of him and some leaking out. "Hahh... y-yeah...~ I wouldn't mind if you... t-took... control..." Junior said, blushing and admitting he liked what he experienced.
 “Don’t worry, I’ll take gooood control, Prince Junior~ Now then, let’s-a-go have a talk with your brothers...~” Mario said with a smirk on his face.
Junior stood up, and more of Mario's cum leaked out, but he didn't mind. "Hehehe... I'm sure they'll be pleased with the results~ I am very talented~" He was almost back to his normal self, but he stuck close with Mario this time. The method may be very unorthodox, but the outcome was the same. That was all that mattered in the Prince's messed up mind.
And so, Mario has become a part of the Koopa Tribe, becoming the first human to do so, having loads of fun with the Koopalings, and even the Koopa King himself had his ass Demolished by the plumber, and  even the Koopa Troopas & Hammer Bros get their asses demolished. But mostly, it was all thanks to Junior who made it possible, and his reward was a HUGE bukkake by Mario and the rest of the male Koopa Tribe. So whoever walks through Junior’s way, watch out, because it’ll be Game Over for you~ in the end, Junior broke the 4th wall, saying “Game Over~” before giggling, blowing a kiss and giving a wink~
The End.