Author Notes: This story was inspired by a tumblr post.

High School AU. Starts out with Derek as a sophomore and goes through senior year. Kate is only a year older than him in this. And Stiles and everyone else his age are sophomores during Derek's senior year.

Disclaimer: This story is based on characters created and owned by the creators of Teen Wolf. No profit is being made. No copyright or trademark infringement is intended. I only have rights to the original characters.

Derek Hale was in love and he was terrified. Not because he was afraid of commitment or anything; he was actually all for commitment. No, he was afraid his twin brother, James, would find fault in his new love interest, and have to leave him, just like with everyone else he's ever dated.

James acting as the overprotective older-by-two-minutes brother started when they were sixteen. Derek was dating Paige, a quiet, unassuming musician. He got ragged on by his teammates quite often because of it; mostly about how an all-star basketball player should date cheerleaders or other popular girls and not nerds.

But Derek ignored them. Every moment spend with Paige made the butterflies in his stomach flutter and a sense of comfort and safety encompassed him. Not to mention that all those stupid love songs that Laura was always blaring at home were making sense now. Derek knew what that meant - Paige was his first love.

Unfortunately a terrible hit and run accident ended their whirlwind romance all too soon. Derek grieved daily for over a month until James dragged him to Paige's grave so that Derek could say everything he's wanted to say to the girl of his dreams, but no longer could. Derek found closure. But James heard and felt his brother's heartache and vowed to never let him get hurt again - at least not due to a relationship.

So when Derek came out as bisexual to the family three months later, along with announcing that he was dating Bryan, a junior, James knew he needed to research this guy, maybe even test him. He wasn't going to let Derek get so attached again and risk all the heartache and pain Derek would suffer should they end badly.

And what better way to "research" than dressing up as your twin and spending time with the new beau? He looked up Bryan's address, borrowed Derek's signature glasses and leather jacket, then headed over to Bryan's.

Now, James and Derek may be identical twins, but there are plenty of minute differences that anyone who truly knew either of them can easily tell them apart. Or at least they should be able to.

Bryan was not one of them. James spent five hours with Bryan and not once had the other boy noticed that he was not spending time with Derek. James was about to make an excuse to leave when instead, Bryan tackled him into the arm of the couch and proceeded to shove his tongue down James' throat. James shoved Bryan away, who thankfully became distracted when his phone began to ring. The distraction was enough time for James to make his escape.

When James returned home, he was immediately knocked to the ground when a hard punch landed on his jaw. Derek had just gotten off the phone with Bryan and had to listen to how his boyfriend kissed his brother, his own flesh and blood. There was a lot of yelling and cursing, but eventually Derek calmed down enough to listen to James explain his actions.

"I just wanted to know this guy, Der. You were so hurt after Paige that I wanted to make sure he was the real deal. I never want to see you in that much pain ever again."

Derek forgave him and broke up with Byran the next day.

Derek didn't date again until junior year, choosing to finish of his sophomore year by focusing on school and basketball. He planned on continuing to focus solely on school and sports, but then he met Jordin on their first day and he just couldn't not pursue her. He didn't love her per say, but he did care about her a lot.

When Derek and Jordin reached their one-month mark, James decided another test was in order. He told Derek about two-weeks in that if things seemed to be getting serious between him and Jordin, that he would put her to the test, too. Derek didn't necessarily like it, but he understood where his brother was coming from. James hoped, for Derek's sake, that she would pass.

But alas, she didn't. Neither did Jennifer, Max, Kara, Julian, or Nishan. Derek was ready to forgo dating again, that was, until, he received an invite to prom from Kate Argent - the most popular girl at Beacon Hills High School.

Prom was still a month away, but Derek and Kate spent tons of time together getting to know each other and plan for the special night. Derek was nervous as prom grew near. He wanted the night to be perfect for Kate - you only get one senior prom of your own, after all - but also because he knew James would test Kate soon. They never officially made it known that they were a couple, but everyone assumed so given how much time they started spending together. Derek knew his brother well enough that being official or not didn't matter.

James waited until the day after prom. He never liked any of the Argents, especially Kate. James witnessed Kate lie and manipulate people on multiple occasions and wondered why she all of a sudden was interested in his brother. Sure, Derek was a catch, but Kate never showed interest in him until now.

Kate had texted Derek asking to meet her at the park for an impromptu date. James was walking by the living room where Derek was passed out on the couch when they text came in. Curious, James checked the text and promptly took the opportunity presented to him.

Dressed in Derek's glasses and leather jacket once more, James met Kate in the most secluded area of the park. Without any warning and barely a hello, Kate rushed him, sending them toppling to the ground. The next thing James knew, he was being groped by Kate with her aggressively kissing him. James fought, but Kate was stronger than she looked. He finally pushed her off and backed away, panting.

"Come on, Derek. Stop holding out on me."

James was glad to hear that Derek hadn't done more than kissing with this girl. "No, Kate... just... no."

Kate grew more and more frustrated until she finally just gave up. "You know what? Fine! I only dated you because I couldn't have your brother anyway!" She stormed away, ignoring his gobsmacked expression.

Now James disliked Kate even more.

Derek was rightfully pissed off when James returned home told his twin what happened.

Come senior year, Derek promised himself that he was not going to date anyone. He was going to focus on school and basketball, get good grades, hopefully earn a scholarship, and get as far away from Beacon Hills as possible.

But a spastic, flirtatious sophomore went and turned his world upside down. The butterflies that he hadn't felt since Paige's death had returned. Love songs no longer mocked him. Sad songs no longer seemed so depressing. One Stiles Stilinski was about to stir up some trouble, and Derek didn't know how to escape, or even if he wanted to.

Derek first noticed Stiles in the locker room when the lacrosse team came in from practice and the basketball team was finishing up after a scrimmage. Derek was leaving when they literally bumped into each other. He turned to apologize and found himself staring in to the most gorgeous set of amber colored eyes that he had ever seen. Stiled muttered out a quick apology before heading to his locker, leaving Derek to continue out.

Derek's interested was piqued and his dreams only served to reaffirm his interest. He needed to find out more about the boy. Through word of mouth, he learned that Stiles was the son of the sheriff; best friend to Scott McCall, fellow lacrosse teammate; and had ADHD, but was still really smart and one of the top students in his class despite the struggle to focus. It wasn't much, but it was enough to tag along with James to the first lacrosse game of the season. When James suspiciously asked about Derek's sudden interested, Derek deflected.

"I just figured it's our senior year. We should spend as much time doing things together that we haven't done before. Make new memories."

James didn't quite believe his brother, but chose to let it go, for the time being. Ten minutes into the game, though, James noticed Derek suddenly perking up. He followed Derek's line of sight and internally groaned when he figured out that Stiles was who his brother was interested in.

He was only a sophomore, but Stiles was well-known in various crowds. He was known to be a bit of a goody-two-shoes since he was the sheriff's son and all, but yet also known to wreak a lot of (harmless) havoc around town and at school. He was wicked smart, but his ADHD and spastic tendencies made everyone think otherwise. What James really disliked about Stiles the most was his pension to flirt with anything with a pulse. Lydia Martin, long-term girlfriend to Jackson Whitmore, captain of the lacrosse team, seemed to face the brunt of the cliche pick-up lines. It was clear that Stiles knew he had no chance with Lydia, and was probably why he flirted so outrageously. James could only hope that Derek wasn't on Stiles' radar, because if he was, Derek was doomed.

While James wanted to keep Stiles as far away from Derek as possible, he also knew he couldn't interfere. Along with his vow to never let Derek get hurt again, he also promised himself that he would allow Derek to start any relationships he wanted. If James just stopped them all from happening, Derek would never find anyone who could be "the one" and make Derek ridiculously happy. So, James sucked it up and waited, still hoping that nothing became of the crush.

To James' dismay, Derek and Stiles started dating the following week. They spent practically all of their free time together, until ten o'clock when Stiles needed to be home and was no longer allowed to have visitors over.

It was one evening when Derek returned home from spending evening with Stiles that he barred his soul to James.

"I love him, Jay. So much. I haven't felt this way since Paige. He is kind, loving, caring. He's a spazz, but it just makes him all the more adorable. He's practically a genius and I wish more people noticed that about him. He flirts a lot, though. It's endearing when it's directed towards me, but I'm furiously jealous when it's not. I wish it was clear how he truly felt about me. He's perfect. I really wish I could keep him forever."

Derek drifted off to sleep on the couch a few minutes later.

The one-month mark quickly arrived and the fear and nervousness began to settle in for Derek. He was terrified. He was in love with Stiles Stilinski. He honestly believed that Stiles was "the one". He learned that Stiles was, like himself, a romantic at heart. So Derek bought Stiles a promise ring since they were both way too young to even consider marriage. But promise and commitment solely to each other until they could - totally doable.

But Stiles had one test he needed to pass before Derek could present his love with the ring.

Derek knew James was visiting Stiles when he woke up, and his brother was gone. James rarely was up before him. Noticing his glasses and leather jacket were missing just confirmed his suspicions. Derek trusted Stiles, but he was still weary about the test since no one ever passed. Derek didn't want to wait until James returned home to find out what happened, so he ate a quick breakfast, got dressed, grabbed the ring, and headed over to Stiles'.

Meanwhile, James arrived at the Stilinski's home. He rang the doorbell and waited for an answer. Luckily the sheriff was already at work and wouldn't need to witness his son showing his true colors. James really wanted to prove that Stiles was just like everyone else; not worthy of his brother.

Stiles answered the door bleary eyes and yawning. "Derek?" he asked, noticing the vague shape and look of his boyfriend. He blinked a few more times to clear his vision.

James was internally congratulating himself on catching Stiles when the boy surprised him and said, "Oh, hi, James." He started and focused back onto Stiles, suspiciously.

"What can I do for my boyfriend's brother so early in the morning?" Stiles asked while moving aside to let James in.

James was hesitant to move. He swore Stiles wouldn't recognize him, but apparently he did. Or Derek warned Stiles ahead of time. So he quickly came up with an excuse while thinking, maybe Stiles can prove to be worthy.

"Just figured I'd come meet you, officially, since Derek hasn't brought you around yet," he finally answered, moving into the house. He hoped he sounded convincing.

"That's nice of you, though I would have enjoyed a heads up, or at least more time to sleep beforehand," Stiles joked, laughing lightly.

They fell into an awkward silence that wasn't extremely uncomfortable like most awkward silences. Stiles finally broke it asking, "So... what would you like to know?"

"Umm..." James was usually a quick thinker, but he was too baffled by the turn of events that his mind was drawing a blank. "I don't know. Anything? Everything? What you feel for Derek?"

"Well, I love him, if that's what you're worried about. Despite a rough exterior, he's kind and gentle and sweet. He loves his family. He's incredibly smart and ridiculously handsome in comparison to myself. He makes me happy. He's wonderful, though I'm sure you already know that."

Before James could respond, there was a knock on the door. James knows it's Derek even before the "Hey, Der!", followed by a kiss. "Your brother's here. Come join us."

Stiles didn't miss Derek's eyes lighting up at the mention of his brother's presence, and when he saw James' worry and confusion, he quickly put together that something was going on.

"Alright, what's going on with you two? Don't try to deny it," Stiles added when he noticed the brothers were about to. "Derek's happy you're here," he directed towards James before turning to Derek, "and James was worried and confused when I brought you in. So, please tell me what's going on."

Derek began explaining how James became an overprotective brother after Paige died, and began testing his significant others whenever they'd near the one-month mark of dating. James picked up explaining how dressing up as Derek brought out various results, but that none of Derek's exes had ever noticed before.

"I'm happy," Derek explained, "not because James is here, but because you obviously know me enough to tell us apart. Like James said, none of my exes had."

There was a bit of an argument between them all over "the test" until they eventually came to an understanding and let it all go.

James gave Derek his glasses and jacket as he was leaving, whispering "he's a keeper" when he gave his twin a hug before heading out the door.

Derek turned to Stiles smiling, which Stiles returned.

"I have a question for you."

"Okay."

Derek got down on one knee, pulling out the promise ring and asking, "Will you promise to be mine?"

Stiles pounced.

Well, I hoped you enjoyed my first Teen Wolf fic. I enjoyed writing it. Feel free to find me on tumblr (thekissballad) and send me any prompts or requests.