Just something cute and short. I don't really know where it came from. Title comes from Him and I from Halsey and G-Eazy.

Disclaimer: I do not own the characters of the title.

"Jace Herondale!" Came a screech from the lab that had people in the hallway raising their eyebrows and looking toward the open door. "I'm going to fucking kill you!" The eyes swung toward Jace Herondale, who was right near the end of the hallway, trying to swallow back a laugh, his eyes dancing, next to a very confused looking Alexander Lightwood. There was a loud slamming noise, and then suddenly a very angry redhead came storming out of the lab, her hair flying around her and her hands clenched into fists at her side.

With black rings around her eyes.

"Wh—" Alec squinted at Clarissa Morgenstern, trying to figure what was on her face, but then his attention shifted to his parabatai, who was suddenly running away at top speed.

"I swear to god!" Clary screamed, skidding past Alec as she turned the corner to run after Jace, passing by a couple of other confused Shadowhunters who quickly got out of her way. "I'm going to fucking—" the rest of her threat was muted as she turned another corner. Alec raised an eyebrow as he looked back down the hall to the lab, where Isabelle was now standing in the doorway. She was clearly trying to bite back a smile, feeling sorry for her best friend but also seeing the funny side of the situation.

"He put ink over the eyes of her microscope," Isabelle called out to Alec, who nodded, understanding.

Then he sighed, because he knew that there was going to be retaliation.

Jace and Clary had been going out for three years now, since Clary was nineteen and Jace was twenty-three, and they were a good couple. They were both incredible Shadowhunters, coming from almost flawless families, and they were paired up most times they were out in the field. Jace had always been pretty shut up, closing people off and not good at talking about his feelings. He was good at playing off serious conversations with a joke, and he acted as though nothing got to him. Clary—like most girls—was very well acquainted with talking about her feelings, but she didn't overload Jace. She had no problem with giving him time to work through how he felt before he spoke with her, and she enjoyed having some fun as well.

However, every now and then, they would start prank wars.

It wasn't often, thank god, but when they started, it was hard to know when they would stop. Sometimes it would only go for a few days, and then it was like they remembered they were adults and moved on with their lives. Sometimes, though, it would go on for a few weeks, and Alec ended up with two pairs of his shoes filled with glue on one occasion when he leant them to Jace and Clary had snuck into Jace's room at the Institute and thought that they were Jace's.

Lydia Branwell had also ended up with purple hair for a day after showering at Clary's after a mission, and had needed Magnus Bane change it back.

Isabelle almost ended up with the heels of a pair of her six inch stiletto's filed off after leaving them at Clary's except Clary had walked in while Jace was executing his plan and had screamed out that Isabelle would probably murder them both if he messed with her shoes.

So because others weren't necessarily safe from the pranks—especially for their close friends—people weren't particularly happy when the pranks started up again.

It took Clary almost two days before the vivid came off from her skin. Rubbing alcohol got it off almost immediately, except Clary had sensitive skin, and paired together with it being close to her eyes, she didn't want to use much of it to come off. She had settled for wearing sunglasses at all times, even if it made her look like a complete idiot.

Even her mother had caught a glimpse of the dark marks around her eyes and hadn't been able to stop herself from laughing.

Clary went with the simple yet effective response of covering his prized motorcycle with multi-coloured post-it notes that Jace took his time very, very carefully taking off so as not to risk taking off any of the expensive paint.

Jace responded by sneaking into her room while Clary was off on a information gathering mission that was doubling as a training session for Max Lightwood and wrapping every single item with tinfoil, right down to her paintbrushes.

Clary had watered down all of the alcohol that Jace kept in the a little cabinet his room.

Jace hacked her work computer and changed her screensaver to an almost completely naked Arnold Schwarzengger and did something so she couldn't change it back until she had one of the IT guys look at it.

Then things seemed to settle down, and everyone was thankful, because Alec and Simon Lewis had ended up with a mouthful of the watery bourbon and they hadn't been impressed. The pair went on a mission together and were away for three days, and even if things could sometimes escalate, they made sure to never take it when they were on the job.

It was Sunday, and it was ridiculously hot because something was playing up with the air conditioning in the Institute. However, Jace had a few ideas on how he and Clary could cool off in his room. Clary and Jace kissed for a while, Clary giggling as she nearly tripped over her own feet as she was backed into his room.

"Come on," Jace bit on her earlobe as he began tugging at her clothes. "Let's get in the shower."

"Why do I get the feeling that I'm gonna get out of the shower dirtier than when I went in?" Clary laughed as she grabbed Jace's shirt and pulled it upward. Jace stepped away from her to take it off and toss it to the floor and then she grabbed at his belt. "Finish undressing, I'm just gonna turn the fan on so that it's cooled down in here by the time we come back in." Jace nodded as he kicked off his shoes and then pushed down his jeans. He was about to take off his briefs when he realized that Clary had opened up his door. "You alright?" He asked in confusion.

"I'm perfect," Clary's smile suddenly shifted to a smirk, a gleam in her eyes, and she flicked the switch for the ceiling fan. Jace realized just a split second before the pink and blue glitter began flying around the room, spinning from where it was piled high on the ceiling fan.

All Jace could do was stand there, watching as the mess glittered throughout his room, all in his hair and sticking to his body. All over his bed, his floor, his clothes that were neatly folded and ready to put away, his shoes, his laptop and desk...

"Magnus?" Jace asked, resignation clear in his voice.

"Uh huh," Clary grinned as she nodded.

"And the A/C? You do something with that?" Jace continued.

"I may have asked Raj to turn it up, just for a few hours," Clary wiggled her eyebrows at him.

"You're a bitch," Jace grumbled, but his mouth was beginning to curl upward in a smile.

"But you la-la-love me," Clary sung out. They stood there for a few moments, the last of the glitter spinning off the ceiling fan and floating through the air, before Jace lunged forward. Clary let out a scream before running out the open door, and Jace took off after her, wearing only briefs and copious amounts of glitter, Clary laughing as she went.

Let me know what you think :)