CHAPTER 1- The lesson.
It was nine years ago...Martha and Caitlyn travelled to France the week Martha turned eighteen years old. Caitlyn was 22 years in that moment. Both sisters were dinning by the sea at a little city in Cote d'Azur , exchanging anecdotes and secrets. It was the birthday of Martha and both girls planned to "burn the city".
"I need to tell you something...the other girl, Mark and me had our first experience in...ehem...oral sex, you know" Martha said, flushed. Caitlyn laughed loudly as she clapped "Ohhhh well well so you just made the STEP, I'm so glad to hear that...And what happened, did he like it?" Caitlyn asked.
"Ohhhh yes, I think so. He exploded so much and told me he couldn't believe it was my first time, but I swear by god it was hahahaha" Martha seemed proud of her achievement. "Oooh yeah gurl! nice job. It may be a matter of genetics it seems hahahaha".
"Genetics?" Martha asked. "Yeah! C'mon! I never told you?" Caitlyn asked with intrigue. "That you were good at oral sex? hmmm maybe" Martha responded.

"Good? I'm not just good! I'm the fucking best hahahaha. All my partners said that I gave them the best heads they ever had" Martha could notice how her sister was so proud as she said that. Martha wasn't very comfy with that...She just told her sister how good she seemed to be in her first experience, and Caitlyn only though of swagger around.
"Well, you know, that doesn't means that you're the best, that only means that those guys didn't had a better experience, ain't I right?" Martha said, a little frustrated by her sister attitude.
"C'mon! don't say that. Do you remember Jenny?" Caitlyn said. "Yeah obviously, she is one of your besties, the girl with that sexy-as-fuck mouth, and the fucking hot boyfriend hahahahaha" Martha said. "Yes, he HAD" Caitlyn responded. "One day, she asked me to do a threesome with her and her boyfriend...well...it was hard for her...because after we two went into a double blowjob, the guy only focused in me, I even got the 'discharge' fully into my mouth. Jenny was so upset after that. Even we had an argument later, she said, literally that I humiliated her in front of her boyfriend and that I should go easier on her. I told her that I expected a better level from her and she lowered the head hahahaha. Well, two weeks later, Jenny told me she broke up with him...but I already knew that, because he asked me to hang out days before...I rejected him of course...but after we fucked a couple times..." Caitlyn concluded.
(Caitlyn and Jenny):

Martha had her eyes wide open. She didn't knew her sister was that mean. But an instinc made her ask only one question: "How does it felt? you know...to destroy your friend's ego...". Caitlyn stared right at her: "The moment when I looked at Jenny and I felt that I defeated her in terms of cocksucking skills was, probably, the moment when I felt more...like a woman, and when I fucked him and he told me that I was a much better fuck than Jenny...well I never felt better before in fact, I felt complete. Hear the lesson your sissy gives you: You aren't a full woman until you smash another woman's ego".
Martha understood that feeling quite fine "Oh, that's what I felt..." She said unconsciously. Caitlyn was surprised. "Oh, I mean..." Martha didn't know if speak. "Well, it was a party I had a couple months ago...and a friend of mine, Ann, and I began to dance in the center of the floor like maniacs hahaha. Well, until we began to pump into each other and twerk and finally Ann fell on the floor. I looked down at her and she got up quickly and ran out. The people murmured things about me being so much better at dancing and have so much sexier body and things like that".
(Ann and Martha):

"Oh, you had your first victory and you didn't even notice it, how cute, hahahahaha" Caitlyn mocked. "Well" Martha started "You did that...more times?" She asked.
"Mmmm yeah, like a couple of times...I always won, if you want to know...And you wanted, huh?" She said in a funny way. "Yeah, I wanted...I was wondering if...you know...for my birthday...you want to...show me your skills? Like meeting someone tonight and..." Martha was trembling as she was saying that words she couldn't believe she was actually saying.
"HAHAHAHAHAHA" Caitlyn laughted. "I was expecting for you to saying...so you wanna learn some tricks huh? Let's do it tonight! And I also could see if you are that...good...as you said before..."
The disco the sisters went was full, they never saw so many people together before and they knew it was the perfect place to find their "judge". Martha and Caitlyn began to dance close to each other. Suddenly they felt alone, just their sister existed in front of them, and they began to dance with more and more ecstasis, trying to outclass the other girl in terms of sexiness.

As the song ended, the girls found that they were exhausted, they began to laugh and hug each other. In a second, like if she got a radar, Caitlyn notice a tall strong guy staring at her and her sister. She bit her lip and said to Martha "turn around, I think we have him...". As Martha turned, she smiled and responded "we have him. Indeed".
The sisters approached the guy and began to flirt with him, trying to catch his attention. The duel began in that very moment and both girl knew it. Within ten minutes, the sisters went out of the disco holding hands with the guy. The easiest conquest of their lives.
As the three entered the room of the sisters, both began to kiss the guy, trying to show him who was the better kisser. Soon, Caitlyn pushed the guy onto the bed and knelt, as Martha did the same, staring at the guy side by side and beginning to undress him, smiling sexily at an aroused guy who couldn't believe what was happening. He was already erect and the girls didn't even touched him.
"Well, before we begin..." Caitlyn started "You must do us a favour" She concluded. "Yeah,,,you'll have to say who do you think...did it...better" Martha continued her sister's word. The guy opened his eyes, understanding a little bit what was happening. "This sisters are testing theirselves...and I'm nothing but the toy...well...I'll be a great toy" He thought.

The cock jumped out of the trunk like a spring as the girls removed it, laughing. "Hmm it's bigger than Mark's" Martha though. Caitlyn bit her lip and tried to grab the cock with her hand, but Martha tried it as well, but the cock was big enough for both hands to stay at the time, one above the other. They began to stroke the dick at unison, while staring sexily at their "judge".
Both girls lowered their heads, smacking cheek to cheek, as they sticked out their tongues, trying to reach the top of the dick, pushing with their heads at her sister's, trying to get the center spot. It was the first time Martha find herself in that situation, but all was kind of obvious to her, every movement was clear, what she got to do was clear for her.
Both girls broke the pushing duel and stared at each other, just moments before they attacked the top of the cock with their lips. They tried to be the first to engulf the whole cock in their mouth, sucking how they could, trying to absorb the dick from their sister and now rival.

Suddenly, Martha manage to get the top of the cock and Caitlyn rushed to engulf the log between her lips. As Martha licked sexily the top, keeping the eye contact, Caitlyn began to go up and down methodically. Caitlyn grabbed Martha by the hair trying to pull her out of the cock. In response, Martha, instinctively, pressed her hand against her sister's head, making her lips widen against the log of the guy's cock. It hurted Caitlyn and suddenly, she broke the contact.
Martha saw that and, by pure instinc, took advantage of it, engulfing the whole cock in her mouth, doing a excellent deepthroat, reaching the base of the dick as she stared, this time, as her sister, who looked at her in awe. Martha kept the deepthroat for like 5 more seconds and then she ended it with a fast movement, bending back her head and making her hair fly, she smiled with her tongue out, looking at her sister.
Caitlyn knew that, in most duels, what her sister did was practically a win, against anyone...but she wasn't anyone, and she attacked the cock, taking her turn at the cock, sucking it expertly, licking the guy's balls and, finally...dealing her own deepthroat.

But Caitlyn was feeling uncomfortable...the cock was huge and the previous pressure on her mouth provoke that tears began to flow down her face. She tried to reach the point where her sister put her lipstick, but before reaching that point, she felt herself choking and had to break the deepthroat. The guy felt how Caitlyn wasn't able to surpass the checkpoint of her sister and it aroused him even more.
Caitlyn stared at the cock, bitting her lip as she saw how her pink lipstick was a little bit, but clearly, above her sister's red one. She attacked again the cock, focused on showing the guy that she was much better skilled than Martha's. But in the very moment she lowered her head, she felt her sister's shoulder pushing her aside, and reaching the center spot. Martha began to suck the cock with hunger and sexiness. with a mixture of moans and laughs. Caitlyn went onto her, trying to counter Martha's brutal attack.
But it was too late. The guy took his cock out of Martha's mouth and began to stroke it frantically. Caitlyn knew what was coming. She looked up at the guy with a begging expression, trying desperately that the discharge fall over her, but she was on the verge of tears. Martha was by her side, smiling and looking directly at the guy's eyes. "Wait a second!" She said, and she turned to Caitlyn, giving her a sudden and fast kiss on the cheek, turning again at the guy, but not without 'marking' her sister's face with her lipstick. The guy has no doubt, but that last picture was the final stone of the duel. He exploded brutally all over Martha's face, who kept smiling and looking at him.

Caitlyn lowered her head as Martha raised an arm in victory. "Well, I have to give my verdict I think" The guy said. "Martha won this...by far, Caitlyn: you should think twice before trying to match her again, you know". As he says that, Martha began to slap Caitlyn's cheek with the wet, satisfied, cock. Caitlyn couldn't stand the humiliation and ran to the batchroom in tears. Martha felt bad, but she remembered what Caitlyn told her before. The sensation was real, she felt more woman than never before. She and the guy fucked for hours. Martha had a boyfriend, but that was different: was a victory fuck. Meanwhile, Caitlyn stood in the bathroom, crying. Her first defeat was her sister's first victory. She feared that this could mean a change of paradigm in the family.
End of Chapter 1.