I do not own Sword Art Online or anything related to Reki Kawahara and Studio A-1 Pictures. This story will be focused on the Kirigaya Siblings, Kazuto (Kirito) and Suguha (Leafa). Also, spoiler warning: M is in case of sexual themes and stuff. Anyway, other than that, enjoy!

Sword Art Online: Kirito X Leafa, The Kirigaya Sibling Affairs

Chapter 1

January 16, 2027 – Morning

Morning came and at the Kirigaya residence, the Kirigaya siblings, Kazuto and Suguha, were eating their breakfast together as they sat across from each other at the table. And as they ate, Suguha looked at her brother who was eating his sandwich while reading some news on the tablet regarding the quests and updates on ALO, or any other MMORPG games, all while he looked as if he was unaware of what Suguha had planned to do with her brother other than going shopping with him.

"Good." Suguha thought, "He doesn't look like he knows what I've planned for him yet. I just need to go to the right place to shop for the best clothes I could find, and maybe get him to notice my sexy side if I showed him the right clothes."

Upon feeling a gaze at him, Kazuto looked up at his sister who had been staring at him for quite some time, before he took his sandwich out of his mouth and asked, "Hey, Sugu, what's up? You've been looking at me like that for quite a while. Is there something wrong?"

"Huh? O-OH! Uh…nope, nothing!" said Suguha nervously, "Nothing at all! I'm just…I'm really, REALLY excited to go out shopping with you! Just the two of us today! Yeah! T-That's it!"

"O-Oh, uh…I-I see." said Kazuto with a sweatdrop before he smiled and said, "Yeah, I'm pretty excited, too. It's almost rare for both of us to hang out in the real world all the time. Well, aside from being at home, anyway."

"Y-Yeah…" said Suguha, before she asked, "Speaking of which, how're you and Asuna-san doing? I heard that she'll be going on her away trip with her family."

"Ah, yeah." said Kazuto, "Apparently, it's a business trip that involves working with a company that's working on a game that's based on the Underworld of Project Alicization after the incident involving the project."

"Oh…" Suguha shuddered and shivered at that, not wanting to be reminded of what had happened when she came to the Underworld.

"Apparently, the company that's working on that game took inspiration from Project Alicization and wanted to work on making a game based on it, and because Asuna was involved in Project Alicization, they wanted her help to work on it as well as her opinion on everything regarding the Underworld." said Kazuto.

"I see." said Suguha, "But wait, couldn't they have just asked for your help instead of Asuna-san, because out of all of us, you've been in the Underworld the longest?"

"Yeah, I kinda asked the same thing." Kazuto chuckled, "But apparently, they only saw footage of what had happened during and after Asuna Full Dived into Project Alicization and not before that. Though I can't say that's surprising since no one knew about it at the time before Asuna came to find me. Plus, they just kinda saw me as insignificant in Underworld, though it's also not surprising since I did literally nothing throughout the War of the Underworld until a little too late. I was in a coma, after all."

"Ah." said Suguha, before she was reminded of her experience and asked, "Um…Onii-chan, b-by any chance, did they…also have footage of what happened to me during my time in the Underworld?"

"Hmm?" said Kazuto with a confused look for a bit, before he remembered that Suguha was involved as well and then answered, "Ah, yeah, about that…they uh…they do, but they decided not to include what happened to you as a reference in their game since it was considered too horrifyingly inappropriate and adulterous, and somewhat pretty gruesome. At least, that's what I heard from Asuna."

"Oh. Oh, good…" Suguha sighed in relief, "Because the last thing I need is to be reminded of what happened to me back in Project Alicization. Or worse, people making a porn game out of it with me in it." That last part made her brother chuckle a bit. She then took a look around the house and asked, "Speaking of Project Alicization, is Alice-san with Asuna-san, too? I haven't seen her at the house at all lately."

"Ah, yeah." said Kazuto, "Asuna invited Alice to come along with her since she was a part of the world Alice came from and because she needed a friend who had the longest experience in that world and to help give the company some good ideas, mostly how the environment and what the world is like from Alice's view."

"Ah." Suguha nodded in understanding.

"Alice was reluctant at first since she didn't like talking about her experience in the Underworld," said Kazuto, "But after some convincing from me and Asuna, she decided to go along with and go with Asuna to help out, as long as it wasn't anything too personal for her."

"Huh." said Suguha, "You know, I'm surprised that Mr. Kikuoka is okay with it."

"Oh, he wasn't at first, since Project Alicization was supposed to be classified." said Kazuto, "But after the terrorist attack at the Ocean Turtle from Gabriel Miller (A.K.A. Subtilizer in GGO and Vecta in Underworld) and his forces, that classification stuff was kinda thrown right outta the window, and he decided to let the company go with it, so long as they don't question him into any further details of the classified stuff. Plus, one of his superiors, the one who funded a lot of money for the project, was really super pissed at him for what had happened because of how much money they had lost and how much it cost his boss dearly, so much that they actually scared him to the point that he relented, saying that he owes them the money that they funded for him for the project."

"Wow." said Suguha, "That must be rough on him."

"Yeah." said Kazuto, "Anyway, because the company will be working on the game based on the Underworld of Project Alicization, Asuna and Alice won't be back for a long while. Who knows for how long, though? Plus, I heard that even Professor Rinko Koujiro will be involved in it, too."

"Ah, I see." said Suguha, as she picked up her mug and drank her milk in it, all while she thought, "So, Asuna-san and Alice-san won't be around to bother the both of us. And if I recall, Rika-san (A.K.A. Lisbeth) and Keiko-san (A.K.A. Silica) won't be around to bother us at all since those two will be helping out with their families with family stuff, not to mention Shino-san (A.K.A. Sinon) will be playing GGO for the whole day. Which means…I can finally have Kazuto-kun all to myself! Perfect! Now no one will have to know what we're about to do!"

"Anyway," said Kazuto, after finishing up his breakfast, "Since it's the two of us and we'll be going shopping for the whole day, we should hurry and get dressed up for the day and check out some clothes that we like and we can buy together." He got up from his seat and said, "I'll go on and get dressed first, so hurry and finish your breakfast so we can go, Sugu."

"Ah, right!" Suguha smiled, "You got it, Onii-chan!"

Kazuto smiled back with a nod before leaving the dining room to go up back to his room to get changed, leaving Suguha to think to herself for a moment, as she thought about the very plan she came up with throughout the night after logging out of ALO to come up for her planning.

"Good." Suguha thought, "Asuna-san is gone and will be gone for who knows how long, and Alice-san being absent in the house is also a bonus. Everyone will be busy with their own thing for the whole day, especially that annoying idiot Nagata (A.K.A. Recon) who won't be around to bother me for the whole day either since he's out of town, thank God. And I already prepared the best and most sexiest clothes that I'll be wearing to entice and seduce Kazuto-kun and for him to check my body out, and I've already found and located the best and most sexiest lingerie store that I could find so that I could further arouse him with, although it took a long while for me to find the right one in the computer, and I've located the best love hotel that me and Kazuto-kun can go to so we can finally make love to one another, just away from our family as much as possible. Then after that, Kazuto-kun will finally…finally be all mine. Perfect! The plan is perfect!" She frowned a little bit and thought, "I really do feel bad about doing this to Asuna-san, about stealing him from her, but…I just can't take it anymore. I have to do this! I love Kazuto-kun too much to stop now!" She looked up with determination and thought, "Right…I can do this!"

After finishing up changing into casual clothes for him to go out with, Kazuto got out of the bedroom and went to Suguha's and waited for her to be finished changing. As usual, he was dressed in black clothing, which consisted of a long-sleeved black shirt underneath the black hoodless jacket that was sipped up to his collar, long black pants with a black belt around the waist, and black shoes, as well as a black bag hanging to the side with the straps hanging around his left shoulder. He waited for Suguha outside her door so that they could go out together. Kazuto took a look at his watch and saw that it had been twenty minutes and Suguha hadn't come out yet.

"Huh." Kazuto thought, "I wonder what's taking Sugu so long? I should probably knock just to check."

He raised his hand to knock on the door, but before he did, the door suddenly opened to reveal Suguha, and immediately, what he saw nearly took his breath away. Suguha was dressed in what he thought might've been the sexiest outfit he had ever seen.

Suguha was wearing a light-green sweater with an open heart-shaped chest area that revealed her cleavage openly, a green jacket, a short dark blue skirt, a pair of green gloves, a pair of black stockings, and a pair of green sneakers. And Suguha was giving out a blush as she fidgeted a little from nervousness while she looked up at him with a cute smile on her face. From the look on Kazuto's face, Suguha could tell that he wasn't looking at her face, but at her cleavage that she couldn't hide.

"W-Well, Onii-chan?" Suguha asked shyly, "What do you think? D-Do I look good? Don't I look cute?"

"H-Huh?" said Kazuto as he got out of his stupor before he answered, "Uh, yeah! Yeah. Y-You…you look great, Sugu! You look…very cute…" "…and pretty sexy." He thought to himself.

"R-Really?!" Suguha lit up before she cheered, "I'm so glad!" Then she went up to her brother and wrapped her arms around his left arm before she said, "Well then, Onii-chan, let's get going!"

"U-Uh, yeah!" said Kazuto as he looked away to hide his blush while trying not to look at her chest, "Right then…let's go."

"Yeah!" Suguha smiled, all while she thought, "Off to our little date together!"

And so, off the Kirigaya siblings went to go shopping, on their date together. Granted, it wasn't exactly a 'date' date, but to Suguha, it might as well be as all throughout their walk, she never let go of her brother's arm. The two had left the house and already made it to their bus stop and waited for the bus to come for them to go out of town together, all while Suguha kept on smiling with her arms around Kazuto who would soon be hers. Kazuto, on the other hand, tried to keep looking away from Suguha so that he wouldn't try to get a glance at his sister's cleavage all the time, only looking back at her from time to time and then looking away. Went the bus arrived at their stop, Suguha wasted no time dragging her brother into the bus and sat at the nearest seat together before the bus began to depart. There were no other passengers on the bus except for the Kirigaya siblings who were seated together like a couple.

"S-So," said Kazuto nervously, "Y-You seem pretty eager to go shopping today, Sugu."

"Yup!" Suguha giggled, "I'm just really happy that I get to spend a lot of time with you, Onii-chan!"

"R-Really?" Kazuto asked.

"Yes, really, silly!" Suguha giggled before she looked at her brother lovingly and thought, "Because, after all…tonight, I'm going to be making you mine, Kazuto-kun. Very soon."

Once the bus stopped at another bus stop, the two began to leave the bus as they were both out in the city with busy streets and people passing by with their daily lives, all while Suguha kept on holding onto her brother. To the people who were passing by the Kirigaya siblings, the two looked like they were a lovely couple going on a date together, and all were oblivious that they were actually siblings.

"So, Sugu," said Kazuto, "Which store do you wanna go to today?"

Suguha giggled knowingly and said, "Oh, I know just the place for us to go shopping, Onii-chan!"

As planned by Suguha, the Kirigaya siblings had arrived at the shopping mall, more specifically, a store that sells sexy lingerie for women. While Suguha was looking around for the lingerie for her to try out to wear, Kazuto stood where he was and looked around while blushing like an idiot, all while the women around the store were looking at him questioningly or with crept looks on their faces. While looking around for the best lingerie, Suguha took a glance back at her brother who was blushing and sweating from all the women's clothes that he was seeing, before she gave out a small smile and then went back to look for the lingerie that she would find to be sexy enough to entice her Kazuto.

Then, once she found what she believed was the best one she could wear to seduce Kazuto, she took the hanger holding that lingerie and then went to the changing room to try it out, before turning to Kazuto and said, "Onii-chan, I'm going to try something out, so come over and wait for me, okay?"

"Huh?" said Kazuto, "O-Oh, uh…o-okay."

As soon as Suguha went in and closed the curtain to change, Kazuto nervously went over and stood in front of the changing room and waited for her, all while eyes were all over the poor boy, making him feel even more nervous. Although there were most of them who did not look at him that way and just minded their own business, though that didn't ease his nervousness.

"Oh, God!" Kazuto thought, "Why am I even here for?! I can't believe Sugu brought me here of all places! Doesn't she realize that I'm a guy and a guy can't be in a place like this?! I don't even know what she's thinking!"

"Hey, Onii-chan!" Suguha called from the curtain.

"H-Huh?!" said Kazuto nervously, "Y-Y-Yeah?! W-What's up, Sugu?"

"I need your opinion on something." said Suguha, before she opened the curtain to reveal what she was wearing, and what Suguha was wearing made Kazuto's eyes almost bulge and made him blush madly.

What Suguha was wearing was black lingerie, with a black bra, black panties with gold strings, and a gold accessory hung on the right side of her thigh, a black see-through silk fabric with black circles on the top with decorated around the abdomen, and a black accessory with gold chains on her right upper arm. All in all, what she was wearing showed more of her skin and fitted her body perfectly.

Seeing his sister dressed in such sexy lingerie made Kazuto blush madly and screamed panickily before looking away from her so that he wouldn't have to see anymore and not look like a pervert. Seeing his sudden reaction made Suguha confused, or rather, she knew but was pretending to look confused.

"Onii-chan?" said Suguha 'confusedly', "What's wrong?"

"S-Sugu!" Kazuto screamed, "D-D-D-Don't do that! W-We're in public, people are gonna get the wrong idea if you showed yourself to me like that!"

"Hmm?" said Suguha 'confusedly' before looking around and 'realized' what he meant and said with a smile, "Oh, oops. Sorry, Onii-chan." She then covered herself again with a curtain before asking again with a blush on her face, "So, uh…about my lingerie…what did you think?"

"U-Uh…w-w-well…" said Kazuto nervously, "I-I-I-I think…I-I think that it…it looks good on you, Sugu…uh…really…really sexy…a-although, if I had an honest opinion…I-I-I-I think that…t-t-that red actually fit you better…"

"Oh, really?" said Suguha, "Hmmm…okay. Thanks, Onii-chan! I'll be sure to get red once I changed back."

With that, Suguha covered herself with the curtain completely to change back to her regular clothing, leaving Kazuto by himself to think about what he just saw with a stupid look and a deep blush on his face, all while he thought, "Oh, God…what did Sugu just show me…s-she…s-s-she looked really sexy and…h-hot…! O-Oh, crap!" As he thought that, he felt a part of his lower half growing as his dick was starting to get hard from the thought of how sexy his sister was, all while he thought, "OH, GOD! WHAT THE HELL?! WHY AM I GETTING HARD FROM HOW HOT SUGU WAS?! SHE'S MY SISTER! WHY AM I GETTING HARD FROM THE THOUGHT OF MY SISTER?!"

Unknown to Kazuto, Suguha was peeking outside and saw that her brother was getting a boner from the thought of her, which made her feel embarrassed yet really happy that Kazuto was starting to think of her that way.

"Well, it's not exactly the kind of reaction that I was expecting the first time I showed him this lingerie, but it's working perfectly." Suguha thought with a blush and a smile, "All according to plan."

So, what do you guys think? Please, be sure to leave a review for me on what you guys think of the story! I hoped you all enjoyed it. Don't be shy and don't just read the story, REVIEW and tell me what are your thoughts of the story!