Jace walked into the Institute, soaking wet and frowning. On his way home from a party (which Clary and Isabelle were still at, fraternizing with some vampires), he'd seen a demon and went chasing it. It had dove into a pond and, Jace being Jace, went in after it. He went to his room and took a hot shower, changing his clothes. While performing these tedious tasks, his mind drifted to Alec. He'd told his sister, Clary, and Jace that he hadn't wanted to go to the party, despite the fact that he had the chance to kick some major demon ass. Alec, despite his sweet disposition, never missed that opportunity. So why had he turned it down?

Jace had offered to stay with him, but Alec turned beet red and insisted he go with the girls, for protection if nothing else. Clary and Isabelle had scoffed but Jace agreed, thought he seriously wondered what Alec was so embarrassed about.

Which was why he was now completely silent as he walked to Alec's room, desperate to find the cause of Alec's earlier embarrassment. He began to hear music as he drew closer, and his eyebrows went up.

Was that… Katy Perry?

He finally reached his parabatai's door, pressing his ear to the wood. Was that Alec Lightwood singing Katy Perry?

Jace opened the door and peered inside. He saw his parabatai dancing around the room, in only boxer shorts and one of Jace's shirts, which was unbuttoned all the way. He was singing along to a song that Jace recognized as Teenage Dream, the one that Isabelle constantly sang around the house. Jace had never thought someone could be precious, adorable, funny, and sexy all at the same time. At least, until he saw Alec singing and dancing to Teenage Dream.

Let's go all the way tonight
No regrets, just love
We can dance until we die
You and I, we'll be young forever

Alec crawled onto the bed, jumping up and down as he sang. Jace couldn't help the big grin that came on his face when he noticed that his parabatai was looking straight at a picture of him.

You make me
Feel like I'm living a teenage dream
The way you turn me on
I can't sleep
Let's run away and
Don't ever look back, don't ever look back

Alec jumped off the bed with a light thud, dancing around his room and moving his hips. Jace licked his lips, the smile still wide on his face. He'd never seen Alec so freed of his careful, nervous facade.

My heart stops
When you look at me
Just one touch
Now baby I believe
This is real
So take a chance and don't ever look back
I'mma get your heart racing in my skin-tight jeans
Be your teenage dream tonight
Let you put your hands on me in my skin-tight jeans
Be your teenage dream tonight

Jace's jaw dropped when Alec danced to that, the smile wiped completely off his face. He wanted to walk away from his boyfriend, pretend like he'd never seen this, because he knew Alec would be mortified if he saw Jace standing there. But, Jesus, Alec was dancing like a high-paid stripper. Jace walking away now would probably mean blue balls for the rest of the evening. So when the song ended, he clapped.

Alec froze, like he didn't want to turn around. He clearly knew exactly who he would see behind him. So, instead, Jace went to him. His arms went around his Alec's waist, and he hugged him from behind.

"Quite the impressive display," he murmured, kissing the back of Alec's neck. "Why don't you dance like that for me, Alec?"

He felt Alec's previously tense body relax slightly now that it was clear Jace wasn't making fun of him. "You never asked."

"I never knew," Jace replied, turning Alec around. He saw his parabatai's face was flushed and his eyes were cast downwards. Jace put his finger underneath Alec's chin and pulled his head up. Alec locked eyes with him, and Jace smirked. "May I request to put my hands on you while you aren't in your skin tight jeans?"

Instead of blushing, like Jace expected him to, Alec smirked back. "Be my guest."

And with that, Jace threw him on the bed and proceeded to do things to him that not only lacked skin-tight jeans, but any clothing at all.