Requested by: anonymous
You and Isaac had been planning Derek's birthday party for him for weeks. He told you not to do anything, but of course you weren't going to listen.
Derek noticed how close you and Isaac were, and he could sense Isaac's feelings towards you. He never suspected anything about a birthday party, only that you were cheating on him.
It was a day before Derek's birthday and you met Isaac at his loft when you knew he wasn't there. You were showing Isaac where everything needed to go, and how to distract Derek in the mean time.
Derek had been at his loft, listening to your plan about someone distracting him. This didn't help the situation at all. He came into the loft, causing you and Isaac to jump.
"Der, what are you doing back?" You questioned.
"What are you doing with Isaac?"
"Studying." You tried to lie.
"I see no books."
"We just finished."
"I can hear your heartbeat, and I can hear his." He said pointing to Isaac.
"I think I know what you're thinking, Derek." Isaac said.
"Do you?"
"Yeah, and I would never do that to you. Neither would Y/N."
"Wait, you think I'm cheating on you?" You butted in.
"I don't think, I know."
"Derek I-"
"Save it, just leave. Both of you."
You didn't say anything as tears streamed down your face. You ran out and got into your car.
—-
"Are we still throwing the party?" Isaac asked you while you were both at Scott's.
"Yes."
"Okay, I'll call Scott and tell him to distract Derek tomorrow."
"Thanks."
"I know you aren't okay." Isaac said to you.
"He thought I was cheating on him, of course I'm not okay."
"Maybe tomorrow he'll realize what we've really been doing."
"Maybe."
—-
Derek's birthday party was officially a go. Scott and Stiles were out distracting Derek, and you, Isaac, Allison, Lydia, and Kira were decorating the loft.
"Wow, my nephew is getting old." Said Peter walking into the loft with Cora.
"You're the old one." You shot back.
"Man, I can't wait to have you in the family one day." Cora said, giving you a hug. You just laughed.
"Okay," you said putting up the last streamer, "let's get this party started."
—-
About an hour later, Scott and Stiles came in, Derek right behind them. Everyone was hiding, but of course Derek could hear the heartbeats.
Stiles turned on the lights and everyone came out.
"Surprise!" You all shouted. Derek looked around and smiled. His eyes then met yours and you weakly smiled.
"You were planning a surprise party for me?" Derek asked you. Everyone was silent.
"Yeah." You said quietly. Derek went up to you and put his lips on yours. You immediately kissed back.
"I'm sorry." He said once he broke away.
"You should be."
"And I am. I'm such an asshat."
"Thanks for admitting it."
"I love you." This was the first time Derek had ever said that. You looked into his emerald eyes and smiled.
"I love you too."
"Okay enough of this stupid romance, can we have cake?" Peter cut in, ruining the moment.
"I made a mistake, Peter's the asshat." Derek said.
"Yeah, a psychotic one."
