This just popped into my head and in my opinion there can't be enough Sizzy fics out there so here it is!

All characters belong to the lovely Cassandra Clare

Sleep

3 am. Izzy's eyes snap open. "Simon, quit watching me sleep! It's annoying!" Simon grins and cups her cheek. "What else should I do? I don't need sleep, besides, I like watching you. Maybe it's something about your face", he mocks.

Izzy groans and covers her face with her hands. "I shouldn't have told you! I knew it was a mistake." Simon shakes his head and pries her hands off her face. He gives Izzy a slight smile and bumps his nose against her. "I'm glad you did. If you hadn't, we wouldn't be here now." He pulls her closer and his legs tangle with hers. "I really like watching you sleep. You look peaceful. You are a completely different Isabelle then." Her dark eyes glitter and she bites her lip. "And that's good?" Simon nods solemnly. "Yeah, all the others only know Izzy the fierce Shadowhunter, but I know Isabelle the sometimes vulnerable girl. I saw her in Idris after… after…" "Max", she whispers. Simon squeezes her sides. "Yes, after Max and I see her every night when I'm in bed with her."

Isabelle suddenly seems breathless. "Do you like her?" He pushes a few stray hairs out of her face and gives her his typical Simon smile. "No…" Izzy's own smile vanishes and she looks quite hurt. Simon leans over her, his face so close that it is the only thing that Izzy can see. He presses a light kiss against her lips and when he says the next words, Isabelle can hear and also feel them. "I think I'm in love with her. Every part of her." Simon swallows her gasp with his mouth and Isabelle decides she doesn't really mind his watching her sleep.