AN: My first fic for TMI! Short, fluffy and not-so-sweet. Takes place in CoG, after they meet Ithuriel. Clary managed to draw a portal, but it was sorta messed up and landed them in the London Institute more than a century in the past. Guest appearance from TID charries at the end. Um, well, I really don't know why I listed humor as one of the genres, but it has something to do with the little scene with the TID characters at the end.

Really, Clary was to blame for all of this.

If Clary had not insisted on going to Idris, he wouldn't have ended up (alone) with her more than a century in the past. If Clary had been slightly more careful drawing that rune to get out of the manor (not that he wasn't grateful they weren't currently crushed), they wouldn't be here. Clary was the one seducing him, the one making him fall in love with her. Clary's rune had landed them here. And it was Clary's fault for being so damn cute, for being so pretty and lovable.

It was Clary's fault. All of it.

Honestly, Jace couldn't remember what this particular argument was about. Ever since the Valentine Incident (which was something he never spoke of), Jace had spent all his time arguing with Clary instead of talking with her. It was sort of a way to keep himself from kissing her and causing a hellishly awkward situation.

Usually, that plan worked. But the keyword rested on usually - meaning, every now and then, it went downhill. Today was one of those days - Jace shell-shocked from discovering he was part-demon, Clary shell-shocked from seeing an angel, with neither of them really thinking clearly.

"You're my sister, Clary!" Jace shouted. Usually, this was where most arguments ended up. Taking a turn and walking down the brother-sister path. Clary's mouth was agape. "Is that what this is all about?" she asked, her voice high. "Brothers aren't supposed to feel like this with their sisters!" Jace hissed. But that was human brothers… maybe with demons, it was normal and okay to fall in love with your siblings.

Clary's green eyes - oh, her beautiful green eyes - widened. "You said you'd be my brother from now on." Her tone was accusing. "Maybe I was lying," Jace answered, beginning to pace. "Jonathan Christopher Morgenstern -" Clary began, but she was interrupted by Jace spinning on his heel and glaring at her.

"Don't. Call. Me. That." His voice was low, angry and hissing like a snake. He really didn't need a reminder of the fact that he was Valentine's son - and, by default, Clary's brother. Something resembling fear flickered in Clary's eyes. Immediately, Jace regretted his words. He sighed. "Look, Clare -" he began, but he was cut off.

"So do you want to my brother or not?" Her words were sudden, confusing, and seemingly pointless. Jace narrowed his eyes and took a few steps closer towards her, to the point there was barely any space between them.

"You're my sister, Clary," he hissed. But, oh, her scent was so intoxicating, and Jace really couldn't help himself, and if that scene with Ithuriel really meant anything, then it meant Jace was part-demon, and demons could be evil and otherworldly and had no moral compass and were like this...

His lips crashed onto hers, and everything went spiralling out of control. Jace felt, more than heard, Clary's gasp of surprise, before she returned the kiss, deepening it and tangling her fingers in his hair.

Jace gripped her waist and pushed her against the nearest wall, pinning her. She was everywhere, her hands running over his chest, his waist, fingers slipping through his belt loop and pulling him closer (which, really, was impossible, seeing how close they were already)...

Clary swung one leg over his hip. Jace, more than happy to help, lift her up by the hips so she could swing the other leg. She was a bit higher up this way, and Jace didn't have to lean down so much to kiss her. Her hands slipped up his shirt, and he slipped his hands up her shirt, tracing her spine and running them lightly over her bra, while she traced the lines and curves of his back. Clary let out a groan, and he responded with one of his own.

He really wasn't sure what would have happened next. Most likely they would have gone even farther - and it was for that reason he was grateful for the sound of someone clearing their throat.

Immediately, the duo leapt apart. Clary fell rather ungracefully to the ground, and Jace stumbled over an ill-placed carpet behind him (but a carpet really can't be ill-placed, can it?).

A young man their age with black hair and blue eyes, like Alec, but at the same time nothing like Alec, stood nearby, eyebrow raised. The girl who had led them here - Tessa, her name was - stared at them. "I thought you said they were siblings?" the boy next to her, odd with his silver hair and silver eyes, whispered. His eyes were as large as saucers, and his jaw looked like it was about to hit the floor.

Tessa stared at them, mouth open and eyes wide. "That's what they said."