Sin Kuromeru is a demon. Yep. She possesses Satan's blue flames too. Is there anything more cliche in the in the Blue Exorcist fandom? Probably not. Also, her mother is dead, she has a tragic backstory, nobody likes her, she's really hot etc. (last part may or may not be a bit too much, sure she's not really ugly but 'really hot'.. i dunno, maybe if she didn't always be so rude ppl would call her hot)

SO YE SHE'S CLICHE I DUN CARE! Also, something important: This is kinda weird. In the story, I decided to make it so that everyone knows what/who Rin is. Basically this is kind of like after season 2 in the anime. So Rin is a demon, the others are KIND OF okay with that, some like Bon ain't used to it yet tho. Btw Sin is flat chested and I have no clue why I decided to ad this now lol.

There MIGHT be Lemons in this story

THERE IS swearing, cursing and more.

Anyways, on to da story!

Sin sat in a sofa, listening to the man speaking in front of him. "So there's this kid. Well there are two, but only one of them will really make you care. His name is Rin Okumura and is your half brother. You are one year older than him. He also has the power of the flames." Sin looked up at the man speaking. His black pupils stared into Sin's dark blue, waiting for a reaction. Nodding for him to continue, Sin started to grow interested. 

"Rin is starting at this school. He'll train to be an exorcist. I decided that I would like if you got to know him a little. You don't really do anything on the days anyways, except for playing that weird game. What was your favorite character's name again? So-Som something?" "Sombra...", Sin corrected a bit annoyed. Mephisto nodded, uninterested. After a while of Mephisto speaking nonsense about Rin and how his family died, etc, she decided to just say it. "So you want me to join his class?"

Mephisto happily nodded. As Sin thought about it, he looked at her features. She'd grown a lot. Her hair which she just two years ago said she'd never have grow long went to her waist and she was wearing a light purple top, which only covered the top half of her body. She wore jeans shorts, which were short enough to make people have a nosebleed by looking from behind. Sin also wore some light purple lipstick, matching her top. Mephisto sighed. Her teen phrase had arrived and soon she would probably be going out doing all kinds of stuff in the late nights. 

"Okay, I guess I'll join. BUT then I would like to have a room away from most people, also not so many (if any) in my dorm.", she finally said. Mephisto grinned, already knowing exactly where to place her. She began to pack her things, such as computer, manga, sketch books, pencils, clothes and so on. Since it was early October, she decided to bring her already bought Halloween costume. It was cat ears, cat eye-lenses, a cat top, cat skirt, cat shoes/heels and some dye. The dye was for her tail, since her cat costume was for a brown cat, not a black one.

"Well then, here's your key to the dorm, your room and the cram school.", Mephisto said. Sin nodded and then grabbed her stuff to leave. "If you need anything you have our key!", Mephisto added before she left the room. She waved her hand to show him she heard, then she left the room. As she walked downstairs she wondered who would be in class. If there was any nice boys or girls, if someone were hot etc. 

As Sin reached school grounds, people looked her way, whispering things like: Isn't that the principals kid? or Ain't that the gay sass? (Yes Sin is gay) or something like that. Sighing Sin walked up to her dormitory. It was a big building, which weirdly enough was basically empty. She smiled and put on a mental note to thank Mephisto. 

Time skip for like two days since it was Friday and Sin wanted to start in the start of a week so ye

Sin woke up to her alarm shrieking. She gently shut it and got up. Mephisto had left her three uniforms, one of them were neatly folded onto the nightstand. Silently Sin dressed, then brushed her hair. She had for some reason showered at 12 in the night so she didn't feel like she needed to for today. Sin had gotten an black and white uniform, in stead of the normal pink and yellow themed. The shirt underneath was white, fitting the black coat very well. Her skirt was black too, and since she thought it was a bit short she decided to go with white leggings underneath. 

As Sin was  about to leave her room for breakfast she heard a voice. "I heard a girl is sharing our dorm with us, is that true Yukio?" The voice sounded like a teen male, about her age. She decided to listen more. Another voice had joined in. "Yep, she stays in this room." The voice was right outside Sin's room now. She decided to be a bit evil. She smacked the door open, right into the face of the unlucky soul in front. "Sorry not sorry for that. Heard your voices outside my room and thought that it was rude of two males to stand gossiping outside a female's room." She then walked straight past the surprised males, ignoring the fact that one of them emitted a strong aura. Maybe it's the Rin kid Mephisto was talking about? 

Since Sin didn't feel like cooking breakfast this morning, she just grabbed one of the pre-made sandwiches in the fridge. Thanking the demon, whose name she had forgotten again, she sat down to eat. After about five minutes the guys joined her. She inspected them closely. The one who wore glasses seemed a bit older than the other, who seemed to be the owner of the strong aura. She stood up and walked up in front of the guys. 

"Hello! My name is Sin Kuromeru. I'm sorry for the bad first expression, I tend to be grumpy when I just woke up.", She introduced herself with a bow. The guys looked at her, before introducing themselves. "My name is Rin Okumura, nice to meet you!", the seemingly younger one said. "Greetings. I am Yukio Okumura, who is Rin's brother. I expect we will see each other through the day.", Yukio said. Sin looked at him, knowing that he would probably be quite boring. 

"So, Rin was it? You smell weird. Are you a demon?", Sin asked out bluntly. The brothers froze for a split second, before Rin started making weird excuses. "It's OK, Mephisto told me. You should have seen your faces!", Sin laughed. Rin exhaled, while Yukio just looked at her like she was a creep. Sin walked up behind Rin, making his nervousness return. Then she smelled his neck, to make sure it was really him that emitted the aura. After that she just happily skipped back to her seat. After eating the breakfast, she then left the room. The brothers just stared after her. 

TIME SKIP TO CLASS 'CUZ WHY NOT!

Sin sat in a hallway, outside the classroom. Rin had already entered and now she was the only one left. Breathing in, she entered the classroom. "Hello! My name is Sin Kuromeru! I will be your classmate from now on. Also...", she added with a creepy smile. "I am a demon", She said, making a scary voice. As Rin stared at her like she was crazy, sin started walking to an empty seat. "PROVE IT!", a muscular guy with a blonde streak among his brown hair exclaimed. Sin grinned even more. She then walked up to him and whispered into his ear. "You sure about that, boy?" The boy slowly nodded and Sin let out a small laugh. She then put her finger in front of the guy's face, pointing upwards. Suddenly a blue flame started glowing on the top. Sin leaned in to the guy, who were now looking really scared. "Believe me now..?"

"Hey! Sin! No creeping out the students." At the sound of the voice Sin turned around to meet Mephisto's gaze. "Oooooooohhh... Eeeh I was just- I mean- Eeh- I didn't-!" Mephisto walked up to her and sent her one of his scary looks. She yelped and ran back to the seat. "I see you met your new classmate? She has a tendency of scaring people, or being rude to them for that part.", he said. Sin just looked at him, a rebellious look in her face. "But don't worry. I made sure that all the teachers know the casting to make her unable to use her spells. She wont endanger you. It's a ring looking thing at the base of her tail-" "SHE HAS A TAIL?!?" "Yes a tail. Anyways, it's there because the tail is a demon's weakest spot. Don't use that to piss her off, or anything else stupid. Got it?" As everyone took in the info and nodded, Sin just sulked. Beside her sat a cloaked figure, seemingly uninterested in Mephisto. Kind of like they already knew. Sin could smell it was a girl, therefore she decided to inspect her a bit. Either the girl was fat, or just had big breasts to hold up the cape like that. 

"Hey, why are you hiding in that cloak. Don't tell me... The Vatican wants you to be a spy on me and Rin?", Sin whispered. The cloaked figure froze a bit, then relaxed. "Heh, they told me you were sharp, but that was unexpected. Yep, I'm a spy. Mostly for Rin, since he doesn't really have much control over his flames." Sin snorted in amusement. The Vatican were really stupid, if they thought that Sin wouldn't notice. Or maybe they just cared as long as Rin didn't notice?

The door opened again, this time their teacher came in. Sin just stared. Rin had started already on Saturday, so he already knew it. That his twin brother was the teacher. "Oi, why is a younger person than me teaching this class?", She asked, quite annoyed. "Since I have enough experience. Now you should learn to call me Okumura-sensei, understood?", Yukio answered coldly. "Eeeeh no. I meant why didn't you tell me this morning, Okumura-sensei?", Sin snorted in a teasing tone. Yukio seemed to ignore her, since he started the class. 

---:o:---

"Hey, ms Kuromeru, are you listening?" "Hmm? Yea I am.", Sin answered. She'd been caught drawing on her desk. "Then answer this: What material is effective against weaker demons?", Yukio said in a matter-of-fact tone. "Silver, but it is different for the stronger demons. Some of them have holy water, others holy wine, hell some even has gold.", Sin answered boringly. Bon, who had smirked when Yukio had asked Sin were now staring at her with his mouth hanging open. Yukio nodded approvingly at the answer. Sin returned to drawing on the table. She was drawing herself, covered in flames. When class had ended, people had walked up to her table and started to ask weird things like 'Why is your uniform black', 'What's your favorite food?' or 'Can you show us your tail?'. Sin just sighed.

"I can show you my tail, IF..", she started. "You wont touch it without my permission. Understood?" The students nodded, and she let her tail hang out from under her skirt. It was about two meters long, about double the length of Rin's. It was pure black, and pretty slim except for the neatly combed fluff on the end. "Can I pet it..?", the guy who were named Shima asked. Sin hesitated a bit, but then she nodded her head briskly. "Oh! It's so soft!", Shima said upon petting it. Shin were blushing like crazy, since the sensation of getting her tail touched by someone she barely knew was new for her. "Can I too?", Rin asked. Sin looked at him weirdly. "Don't you have a tail to pet yourself?", she asked. "First, that's just weird. Second, mine isn't really as neatly cared for. What soap do you use? Or do you just use shampoo?", Rin said. Sin nodded briskly and Rin took over petting. "Whoa it is really soft!", he exclaimed. Soon everyone had petted Sin's tail, which were now back under her skirt.

"Oh, by the way, or well not really, wanna eat with us?", Bon asked. Sin nodded her head, deciding to go a bit friendly with them first. They walked to the cafeteria together, enjoying each others company. Sin decided to walk up behind Rin, to get a closer look on his tail. It was not really cared for and you could see it was filthy just by looking. The ring on Rin's tail was golden colored, while Sin's was silver. Rin's tail was swaying right in front of Sin, his tail being so vulnerable. Sin decided to be evil, so she grabbed his tail earning a surprised yelp of pain. Rin turned around and shrieked 'What was that for' and such. While Sin and the guys burst out laughing, the girls just looked at her weirdly. 

"I just had to, it's your fault for swinging it in my face! And dude, you should seriously wash it, now my hand is super filthy.", Sin exclaimed. Rin just snorted and brought his tail closer to him, while Sin kept laughing. When they reached the cafeteria, Sin looked at all the expensive foods. Deciding upon a first class Hamburger for thirty thousand yen, she licked her lips. She ordered using the card Mephisto had given her. About thirty seconds later, the hamburger had arrived on a plate. Sin grabbed it and walked over to the others in the class, who had brought their own lunch. 

After lunch, the class had an one hour break. Sin was quite energetic for the day, so she decided to play chase with Rin, who agreed so they could see who was the fastest, or well, most agile. Sin started as a chaser, knowing immediately what method she would use. Rin had started running, while Sin looked after him giving him a ten second advantage. She immediately took of when she'd counted to ten. Rin was ahead of her by about fifty meters. Now forty. Thirty. Twenty. Rin took a sharp turn, gaining a bit of distance. Fifteen. Ten. Five. Sin reached out her hand, tagging him. "You are it!", she screamed then ran past him. Rin let out a growl and changed to a quicker pace. He had almost caught up to her when they reached a park. Sin smirked and jumped through one of the small windows of the fake house. Rin ran around it but didn't see Sin. "Yohoo! I'm up here." Looking up, Rin saw Sin on the top of the play-house. It was about ten meters high (not kidding) so Rin wondered how she got there. Rin began climbing it, but when there was a meter left Sin jumped over him into a tree. Rin jumped onto it and the chase began. 

About a minute later Rin began to grow a bit tired of running and jumping through the trees. "Time out!", he yelled from behind Sin. She stopped and turned around, to see Rin standing leaning on the trunk of a tree. He was already panting hard. "Jeez, I thought you would hold out a bit longer. Well well.", Sin said a bit disappointed. She jumped between the branches, until she reached Rin. She looked at her half brother with disappointment clear in her eyes. She had clearly hoped that he would have put up a match. Sighing, she sat down beside him. She then grabbed a comb and some spray balsam. She began to spray it on Rin's tail, then began to (try) combing it. Rin twitched in pain as she got to a big piece of tangled fur. Sin grabbed it and began to comb through it, ignoring Rin's yelps of pain. 

After a while Sin gave up. "Well, seems like I'll have to help you wash it. We can use my shower room, since I have the right kind of shampoo." Rin immediately began to blush. "W-what?", he said. Sin grinned at his embarrassment. "Well how else? It's not like I haven't seen you naked anyways. Close the windows in the room before you drop the towel.", She explained. Rin's blush grew even deeper. "Also, if you can't even keep running full speed for a minute, how the fuck do you have those abs?", Sin continued. Rin got quiet. "Dude I'm just joking. YOU SHOULD SEE YOUR FACE! YOU ARE REDDER THAN YOUR OWN BLOOD!"

---:o:---

"Hey, Rin. If you wanna get the tail done before Yukio comes home, I recommend we start now. Otherwise it would be hella embarrassing, you know.", Sin shouted from outside Rin's room. Rin, who had been playing with Kuro, immediately answered. "Okay! Coming. Let me just grab some clean clothes." Sin stood outside the door, listening. She knew that was just an excuse. "Kuro what do I do? I don't want to get showered by a girl. Especially not my tail!" "Well just let her do it. Otherwise she will be nagging you for ages, plus after that you will probably know how to do it yourself.", a new voice said. Sin recognized it as Kuro's, Rin's familiar. Sin sighed. After a while, Rin opened the door. He had an embarrassed look, showing that he did not like the idea of getting his tail showered by a girl.

As they walked quietly too the girls bathroom, Rin grew even more nervous. Maybe I should just run..?  Sin sighed. "Let's just get this over with. And you don't really have to be embarrassed. I have showered Mephisto, so you shouldn't be anything. Ugh Mephisto ruined my innocent soul when I had to shower him..." Rin laughed at Sin's story. When they entered the bathroom Rin immediately let out a gasp. It was a lot bigger than the boys. The changing room were one thing. Then the shower room got into view. It had like fifteen showers, two bubble baths, one vending machine selling different soaps and makeup AND a sauna. 

"Well then, undress. I will shower too, that way you can do a bit on your own and I will just show you the easy parts.", Sin casually said. She began undressing and was soon naked. Rin looked away as soon as she had said those words. "What's taking so long?", Sin asked. "Well you're a girl.. Naked.. And I am a boy..", Rin said. "I don't care about that. I'm flat chested anyways. Now hurry before Yukio gets home and starts looking for us.", the girl answered. Rin sighed, and undressed until he were only in underpants. Sighing Sin raised her hand, ready to snap her fingers. "Hurry before I burn them."

---:o:---

When Sin and Rin finally were in the shower, Sin motioned for Rin to sit at one of the benches under a sitting-shower (A/N they have those where I live, okay?!). While Rin sat down Sin started the water, making sure it was an OK temperature. She began with letting Rin wash his own body and hair, while she did the same. Then when both had the tails left, Sin walked up to Rin and sat beside him. She had a bottle of shampoo in her hand, which she put on the bench. "Now listen to the instructions I give you.", She said. Rin nodded, blushing. He had made sure to cover his crotch area with bubbles, but of course Sin didn't even look that way. 

"First up, grab about this much soap into your hand. Then slowly begin at the base, right after the ring, to scrub the tail. Scrub it all the way to where the tail grows broader and has longer fur.", she instructed. She began showing with her tail, ignoring the fact that Rin was staring at her butt in stead of tail. "Now you do it", she said as she reached the spot she had mentioned. Rin recalled what she had said and began scrubbing. "No, you have to do it longer there. You shouldn't be able to see the fur through the bubbles. Like this.", Sin said. She started scrubbing on Rin's tail, making him do a weird sound of surprise. When she was done she motioned for Rin to do the remaining part. She watched him do it, making sure he didn't miss any spots. Earning a 'good job' when Rin was done, he then looked at Sin to show him the next part. 

"This is the harder part. I will do this one for you for the remaining three days, since your fur is too messy for you to do it yourself. I can let you try on mine though, since if you fail miserably it will be easier to fix. Now look closely how I do.", She said. Rin nodded, turning his tail up to Sin. She began massaging it, trailing her fingers around in a weird pattern. Rin watched closely at the movement. Up, left, down, right, repeat.. When Sin was done he asked if he could try on her tail. She nodded as he took some shampoo on his hands and turned to the side. Sin's back were to Rin and she were flicking her tail in front of him. He grabbed it, making her turn her head backwards a little. He then began massaging it the same way he'd seen her do it. As he reached the tip though, Sin let a small sound of pain escape her lips. Rin immediately stopped, sending her a curious yet concerned gaze. 

"It's okay. I just cut myself on my tail when I was training with my knives. It stings a bit, but just continue.", She said. Rin looked at her for a moment then continued. Every time she twitched in pain he felt like he should stop, yet he continued until he reached the very tip. He did as she had done at his tip, swirling it a bit. Sin let out a small yelp of pain. As Rin released, she had immediately taken her tail for inspection. "Not bad. But not good either. We will have to try again tomorrow. Now you just have to shower away the shampoo with water."

Rin nodded. He felt relieved, finally the backwardness would be over. He stood up and went to one of the higher showers, without a bench under it. He showered of the water and Sin did the same in the shower behind. When he shut of the water she threw him a towel. He grabbed it and looked at her. She had a nice hue, a little tan still left from the summer. He couldn't spot a hair growing anywhere except for the brown one on her head and the dark brown on her tail. His eyes trailed downwards, towards her crotch. Realizing this, he immediately looked away blushing. He began to dry himself. 

"Heh, not even the almighty son of Satan manages to avoid looking at her shining beautiful body!", Sin smirked teasingly. Rin looked up from under the towel and playfully tugged at her tail. Which was not a good idea. As they left the shower room Rin had a big red mark on the side of his cheek. Although he kind of deserved it, he thought it was as much of Sin's sin (lol) by teasing him in that way. 

"Guys! I'm back." Rin and Sin both widened their eyes. Both of them were only wearing towels around their bodies. They looked at each others and at the same time shrieked: "WAIT A MINUTE! DON'T ENTER RIN'S/OUR ROOM!" They ran into the room, where Rin quickly put on a pair of underpants and a shirt. Sin had brought underwear to the shower room, so she was wearing that and a grey t-shirt Rin just threw to her. The door to the room slammed open showing an angry looking Yukio. "What's going on here?", he asked. As he saw that neither of them were fully dressed, both showing underwear, he started starting at Rin. 

"Dude I helped Rin wash his tail since he apparently didn't know how to do it right. We were about to go get some clothes when you barged in, so we just panicked and threw on what we saw.", Sin easily explained. Yukio looked at her for a moment, then back to his brother. "Is this true?" Rin nodded blushing. Yukio sighed. He then threw clothes at Rin. Sin just looked at him in surprise at the action. 

---:o:---

The next day, Rin and Sin walked to class together. Sin had managed to get him to allow her combing the fur, which now was starting to look neat. The fur was all brushed, pretty clean and there were no filth in it. At the end there was also a small braid that Sin had made. They walked through the corridor, to their classroom where they waited outside since they were early. When the classroom got unlocked, they walked in and sat beside each other in the middle at the front. Sin had her tail up and was fiddling with it, braiding it in the longer furs too. She has longer tail fur at the tip, reaching to twenty centimeters at it's longest. 

The door opened and the two demons looked up to see Konekomaru and Bon, both surprised to see that they weren't first. They looked at the two people in front. Sin had returned to braiding her tail, while Rin just looked at her while she was doing it. Rin flicked his tail to his face. At it's longest it was only ten centimeters. He let out a sigh and began dragging his fingers in it which felt surprisingly good. He kept massaging himself, having a pleased look. Sin looked up and tried it herself, realizing how good it actually felt. Soon the two demons were massaging each others tails, enjoying themselves. 

As everyone were in class except for the teacher, Sin couldn't help but to notice their stares. She quickly turned towards the senders. Bon and Shima. "What?", she asked. Bon just looked away while Shima said "I wish I had a tail.." in a weird voice. Sin mentally face palmed. The door opened and the teacher came in. He looked the two half-siblings through slit eyes. Sin sent him a glare, then continued massaging Rin's tail. She had found his 'spot'. As soon as she had gotten there Rin had stopped his movement and when she began massaging it he fell back into the chair clearly enjoying it.

"Well then, class. Today we will go through a demon's weak spot. As you obviously can tell, it's their tail.", Yukio began, rolling his eyes at his twin who looked like he was in heaven. Sin looked at him. "What's a humans weak spot?", she asked. Yukio glared at her. "What? There has to be some place? And since you know ours, we should know yours!", she prodded. When Yukio still didn't answer she pouted. Then she held her hand up, ready to flick her fingers. "Would pain help you say it..?", she murmured. Yukio raised an eyebrow. Then he sighed. "Humans have different, depending on gender. You will have to ask Mephisto, since I am not comfortable in the subject."

As Sin looked at him angrily, she squeezed Rin's tail a bit hard. He yelped and brought his tail away from her as he sent her a look. Yukio sighed. "Well that's a example. Anyone care to try it?", he said. Sin immediately brought her tail under her skirt as Bon raised his hand. He walked up to Rin who sent him an 'I dare you' look. As Bon grabbed Rin's tail softly, ready to squeeze it, Sin took out her tail and slapped it into his face. "If you get to freely abuse Rin's or my tail, I would like to freely abuse you too." She ignored the glare sent her way and once again hid her tail when Bon was about to grab it. "I'd recommend going back to your bench if you don't want me to burn your tiny little branch to ashes."

"OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOHHHHHHHHHHHHHHHHH! GET BUUURNT! (A/N: may or may not be a pun)"

Anyways, this wasn't really a cliffhanger but I want to save it here since it will be easier to do next chapter then. I hope you liked it, it has about 4.8 K words. Bai bai!!!