Author's Note:

This is part of a songfic challenge where I have to create 18 songfics. This one is number twelve and its a Buffy the Vampire Slayer crossover with Mortal Instruments. The song I chose was This World by Selah Sue which I thought was appropriate for both the fandoms since they live in crazy worlds. Note that I only saw the movie of Mortal Instruments and I just started the first book and I only am on the first season of Buffy the Vampire Slayer so forgive me if I'm off about a few things. Its an alternate universe anyway.

Buffy was stressed. She sat in her dorm room only doing homework. She wanted something to do. All the other kids were at mixer, while Buffy was not allowed to go after she and a few friends attacked some vampires, that were in the form of humans. She watched the other students from her window enjoying the night, while she felt isolated.

She did not hear the door open since she was so stressed out. She felt darkness over her eyes and a voice that asked, "Guess who?"

Buffy let out a small laugh and said, "I know its you, Jace."

Jace let go of her and she turned to face him. "What are you doing here? I thought we were under dorm arrest so we couldn't leave for the night." She said.

"I decided to bend the rules a bit." Jace said. "besides I got lonely."

"I'm kind of lonely too." Buffy said.

"You also seem tense." Jace said. "Lay down and I'll give you a massage."

"You give massages?" Buffy asked, crossing her arms.

"Just keep it a secret between you and me." Jace said with a wink. Buffy got on the bed, on her stomach so her back was facing him. "and besides since we are a couple, I thought tonight should be special since we are not enjoying the party like the rest of the group."

"Oh really, then show me what you can do, massage boy." Buffy teased.

"Take off your shirt first." Jace said.

"Oh right, sorry. I never done this before." Buffy said, taking off her white cotton halter top. Then she lay back down. She had her ipod on her speakers and put on some relaxing Rhytjm and Blues.

"Now just relax." He said as he began moving his arms against her tight muscles. "your tight."

"I know, all this slaying has gotten me really stressed lately." Buffy said.

"I can see that." Jace said, pressing on a pressure point. "Do you remember when we first met?"

Buffy said a faint, "yes."

Three new students entered Sunnydale as if they were models strutting down the runway. They were gorgeous people. There were two boys and one girl. Everyone stopped to look at them since they were so different. They had some kind of aura that struck one's attention. Unlike most people at Sunnydale, they dressed in a more seductive gothic style while the normal students wore bright vibrant colors and (sometimes) very conservative clothing.

They were all about the same age and all were in Buffy Summer's home room, which was english. "Class." The teacher announced. "I'd like you all to meet three new students." He came to one boy who had jet black hair. "This is Alec Lightwood." The boy just shrugged.

Then the teacher came to the girl who looked fairly similar to him, same hair color, same olive skin and dark mysterious eyes. "This is his younger sister, Isabelle Lightwood." The girl waved, a flirtatious wave in no one in particular as Alec and the other boy who was tall with pale skin and blonde curly hair and golden eyes rolled their eyes.

Xander Harris, Buffy's best male friend whispered to her, "I think she likes me."

"Puh-lease." Buffy's other friend, Willow said, crossing her arms.

Buffy's eyes were caught on the blonde boy, who the teacher introduced "and this is Jace Herondale. Please make yourselves at home here. You may sit where ever there is an open seat."

Buffy glanced at Xander who was sitting next to her and motioned for her fingers for him to move. But Xander mouthed "why?" Buffy just gave him a look saying she was reserving that seat ONLY for Jace. Xander didn't move. Instead he took a seat next to the school's bitchy Queen Bee, Cordelia Chase, who flirted with EVERY male that Buffy had her eyes on.

Xander didn't get to be near Isabelle either, she sat with her brother and a bunch of other students. "Look what you made Isabelle do. Now she is sitting with the even less popular people than we are." Xander whispered as the teacher continued his lecture.

"Well thats what you get for not letting Jace sit next to me." Buffy whispered back, annoyed with Xander.

Later at lunch, Jace was clearly annoyed with Cordelia and her preppy way of flirting with him. Buffy could tell he was clearly not interested.

"Maybe since he is alone, you should talk to him?" Willow asked.

"Okay." Buffy said, adjusting her knee high skirt and then slowly approaching him. She noticed he had odd tattoos and decided to compliment him. Thats how you get a guys attention...right? "Hey I'm Buffy." She introduced herself.

"I'm Jace." He responded, indifferent.

"You have some cool tattoos, what does those symbols mean?" Buffy asked.

Jace's eyes widened. "You can see them?" He asked.

"Duh, they're in plain sight." Buffy answered. "I mean everyone could see them."

"Only hunters and demons can see my relics." Jace muttered.

"Relics?" Buffy asked.

"I gotta go." Jace said, fleeing the scene since he knew he was in deep trouble if he told anyone what he is or what he does.

"Well that didn't go so well." Buffy said to Willow.

"Maybe he is just shy, being the new kid?" Willow said. "Give him some time. I'm sure he'll warm up."

"Why are you bringing that up?" Buffy asked.

"No reason in particular." He said. "I just thought since we've been together for eight years…"

"That you want to get some?" Buffy asked.

"If thats what you call it then yes." Jace answered.

"Tell you what, if your massage is amazing as you say it is, mabey I'll let you have access to do so." Buffy bribed.

"Fine, do you have any essential oils?" Jace asked.

"I have a few in the bathroom." Buffy said since she did believe in some forms of holistic healing.

Jace went in the bathroom and found some rose oil and mixed it with a mint scented lotion. He sat on her tailbone and put the infusion on his hands onto her back.

"You have strong hands." Buffy commented.

"Why do you think I'm so good at shadow hunting?" Jace asked. "I work out almost every single day."

"Oh please, you aren't as good as me. Remember when I schooled your ass on shadow hunting?" Buffy teased.

A few nights later Buffy was being attacked by a demon in the hallway of the girl's dorm. It was really late in the night so everyone had to be asleep, that or left the dorm from fear. Buffy had no weapons and was finding herself getting weaker since the demon was feeding off her energy.

She sank to the floor as the demon grabbed her by the neck. "Your mine." it whispered but then Buffy heard a crack of a whip.

"Not for long." A welsh voice said. Buffy looked to her surprise to see Jace, Isabelle and Alec.

"Guys, you gotta get out of here. I'll take care of this, I swear." Buffy pleaded.

"No your just a mundane. We're slayers. We know how to handle these." Alec said, forming a battle stance.

"I'm not a mundane." Buffy weakly argued. "I've been slaying these things since you were probably in diapers."

Jace gave her a hand to help her up which she gladly took. Then he said coldly, "Then you slay the demon. After all you're so high and mighty."

The three other slayers watched as Buffy tried to catch her breathe for a moment. Then she ripped a strip of wood from the banister, forming a stake. The demon formed snakes from its back, trying to distract the slayer, but dodged all of them.

Isabelle was about use one of her ruins to bind the demon, but Alec stopped her. "She doesn't need our help, remember?"

"But she seems weakened, can't we for just a little. I don't want to leave her here." Isabelle countered.

"She says she has been doing this longer than we have, so why not take a break and let her do all the work?" Alec said.

Buffy cartwheeled and tumbled to the demon's core where she stabbed it with a stake, turining it into dust. Then looked at the others. "How do you like me now? Still think you're better than me?"

The three other slayers looked at one another then at Buffy. "Where did you learn to do that?" Isabelle asked. "Are you a shadow hunter as well?"

"Me? Yeah, but I'm better with vampires than anything else. That creature is something I never seen before." Buffy answered.

"So that explains why you can see my ruins." Jace commented.

"You mean their invisible to those who are not one of us?" Buffy asked.

"You didn't know that?" Isabelle questioned.

Buffy shook her head. "I just use martial arts and a wooden stake, and thats about all I need." She said.

"Buffy, is it?" Jace asked. Buffy nodded. "Tell me, are there any other shadow hunters here at Sunnydale?"

"Just me." Buffy said. "I would always like a team to work with since its hard work being the only shadow hunter here."

"But if you're a shadow hunter, how come you don't know anything about ruins?" Alec asked.

"A guy from my old school told me I was a chosen one. That I can see demons and fight them." Buffy answered. "He said he was a watcher."

"I see." Alec said, unamused.

"Well count us into joining you. We could always use ectra people to slay demons." Jace said.

"What?" Alec said appalled. "No, we work just the three of us!"

"We can't Alec. We can't afford to lose another slayer in our group. The only thing we can do is recruit." Isabelle said.

Alec said nothing and left.

"Yeah, I'm still going to claim my revenge on you one day." Jace said.

"Oh? And how you going to do that?" Buffy asked.

"By doing this." He said, moving her hair so he had access to kiss the back of her neck. She let out a soft moan. "I'll have you screaming my name at the end of this."

"So have you done this before?" Buffy questioned.

"No, but I think I'll get the hang of things eventually." Jace answered.

"Then I wish you luck." Buffy said.

She struggled to turn over but couldn't since his weight was on her. He snickered at his attempt and unhooked her bra as he began to fondle her breast. She moaned again.

"Enjoy this don't you?" Jace asked.

"Dammit Jace." She muttered in between soft moans.

He got off her and flipped her over so she can face him. He sucked on her neck as she ran her fingers through his hair. Then he removed his lips from her neck and kissed her passionately, pushing her back into the pillow. She pulled off his hoodie followed by the tank top.

She broke the kiss and asked "No ruins tonight?"

"I wasn't planning on fighting any demons tonight." He answered.

"Aw, but you're so much sexier with them on." Buffy whined.

"I'll keep that in mind next time." Jace said, and returned kissing her, slipping his tounge in her mouth. They battled for dominance and surprisingly, Buffy won.

"Beat me again, Summers." Jace said, in mock frustration.

"Good, does that mean I get top?" Buffy asked.

"Since when did you become so naughty?" Jace teased.

Buffy blushed and said in a cutesy tone, "i don't know." He then noticed his pants were unzipped and her hands were slowly pulling them down.

"Fanfiction again?" Jace asked.

"Maybe." Buffy teased, rolling him so she was on top and pressed her breast in front of his face. "Like what you see?"

"In fact I do." Jace said, caressing her soft flesh and then bringing one to his mouth so he can suck on her.

Buffy arched her back and let out a moan. Jace smirked and swirled his tounge around the nipple and then switched. Buffy noticed that he was getting hard and more erect and soon he would be untamable.

Jace rolled Buffy over so she was on bottom again, frustrated with his action. He took off her skirt and toyed with her panties. She let out another breathy moan.

"Your so adorable." He teased her.

"And you're so evil." Buffy retorted, she wanted to toy with him more, but he wouldn't let her.

"Am I?" He said, kissing her thigh.

Buffy hissed a "Yes." And he snickered to her response. "Dammit, Jace."

He took off her panties and proceeded to spread her legs and lick her like a cat with milk.

"Jace…" She purred, enjoying the euphoric touch that he brought her. She wrapped her legs around his neck, to deepen the pleasure.

The moans were loud, but only to become louder later with the grand finale. She reached her mid climax with her juices stained across the white cotton sheets.

"You taste good, Summers." He said, licking his lips.

"I wonder how you taste." Buffy said, sliding down his boxers. He was long and thick. She was a bit intimidated but knew she had to overcome the fear of the male anatomy eventually and took him in full force.

"Didn't know you were so pushy." Jace muttered in between moans. He had to admit this felt amazing. Her warm mouth against his aching flesh felt as if an angel got his wings, pleasurable.

Buffy choked and gagged every so often, only because she was not used to having something so large in her mouth, however eventually getting the hang of it, and sometimes even stroking his balls for more of that good feeling.

"Buffy…" He moaned. She kept going until he felt that he was at his end and that it was time to wrap this show up. She lay back down and wiped his semen off her lips. "Bitter but tasty."

"Are you ready for this?" Jace asked, stroking his girlfriend's strawberry blonde hair.

"I've sleighed vampires, Jace. I'm pretty sure this is nothing compared what they do to mortals." Buffy said like a smart-alec.

"Your brave, Buffy." Jace said, positioning himself to enter her wet soaking entress.

"I have to be or else no one will take me seriously." Buffy said.

He finally entered her and she let out a loud shriek of pain as if a victim of a horror movie killer. Glass could of broken, but none didn't. Jace didn't even care if the whole school heard them in the heated moment. They had the right to know. Slayers are meant to be with OTHER slayers and NOT mundanes.

Eventually Buffy started calming down. Not because Jace's lips were pressed onto hers for a brief moment to shut her up, but because she finally felt the ecstasy to kick in and she loved every minute of it.

"Jaaaace." She moaned loudly. "Harder, faster, mooooorre."

Jace's thrusts got faster and harder and Buffy's moans were uncontrollable. Until she finally reached her climax and shortly to be followed after Jace's orgasm.

Jace kissed her forehead. "That was so much better than any dance."

"Yeah." Buffy agreed and she drifted off to sleep, having pleasant dreams.