(Sam and Dean aren't related.)

Sam watched as Dean and Cas walked into the school, holding hands.

Senpai, why aren't you with me? He thought as he glared at the back of Dean's head. I'll love you more than he ever will.

Cas and Dean shared a quick kiss before going off to their seperate classes.

Sam followed after Dean, seeing as they had the same class together, so everything looked normal.

Little did everyone know, Sam was planning something.

Something... Dangerous.

That afternoon, Dean was still at the school. He had practice for track everyday after school and he would go and shower then leave.

Coincidentally, Sam also stays after school. He had a book club that he was part of and would stay everyday as well.

Sam decided to take his plan into action. After his club was over and Dean was in the shower, Sam went to the Home Ec room, found a frying pan, and headed to the shower room.

Sam walked in and heard one of the showers running. Smirking a bit, he hid in the shadows and waited for Dean to finish.

When Dean finished, he had a towel around his waist and walked out to his locker. Something felt wrong, but he ignored the feeling.

Dean got dressed and that's when Sam struck. He hit Dean over the head and knocked him out.

With a smirk, Sam grabbed Dean's bag and hid the frying pan. He checked outside the school to make sure no one was around, and with haste, he carried Dean's bag to his car.

He went back to the showers and picked Dean up. He made it look as if Dean was sleeping, and Sam was just helping him home. He did it just in case anyone saw them.

Smirking, Sam shoved Dean in his car, got it and quickly drove off.

Senpai, I'm doing this all for you.

Dean woke up, head throbbing and in a dark room.

He looked around and whimpered. He tried to move, but couldn't move his legs and arms.

"I see you're awake."

Dean looked up and looked around for the voice. "H-Hello?"

Sam stepped out of the shadows, an sinister smile on his face.

"W-What do you want from me?"

"You have someone that I want. And I'm going to get him." Sam duck taped Dean's mouth and picked up a knife. "This is going to be fun."

Dean's eyes widened as he watched Sam twil the blade. He shook his head vigorously, but it was no use.

The next day at school, Cas was sad that he didn't hear from Dean all night. And when he got to school, he didn't see Dean at all.

With a sigh, Cas started to head to his class.

"Cas!"

Cas turned around and saw a tall boy heading to him. He recognized the boy as Sam. He had a few classes with him before. "Oh, hello Sam. How are you?"

Sam stopped in front of him and smiled nicely. "I'm fine. But, how are you?"

"I'm doing alright."

"Are you sure?"

"Yes... What do you mean?"

"I, um... Heard about what Dean breaking up with you."

"He didn't break up with me."

Sam tilted his head. "Really? That's the rumor that's been going around."

Cas shook his head. "No, he didn't." At least, he thought Dean didn't. He took out his phone and went to his messages. His heart dropped when he saw the obvious break up text from Dean. "O-Oh my god..."

"Cas, you alright?"

"He... He broke up with me!"

Cas started to cry while staring at his phone.

"Oh, Cas. I'm so sorry." Sam gently wrapped his arms around Cas, hugging him tightly. On the inside, he was giddy that he was touching his senpai.

Cas felt safe in Sam's hug. He didn't know why. So, he hugged back and cried into Sam's chest.

Months later, Sam had cleared all signs of Dean ever going to their school.

Him and Cas had also been hanging out a lot more. They formed an amazing friendship.

One day, Sam got brave, and asked Cas out.

He was excited when Cas said yes.

I got a date with Senpai! I got a date with Senpai! Sam thought with a giggle as he got ready that night.

No one better try messing with my Senpai.

I love my Senpai, yes I do. He's for me. Not for them.

So, horrible chapter. Barely had any Sastiel in it, but I couldn't resist making a Yandere!Sam!

The inspiration I got to write this chapter, came from Yandere Simulator.

I also tried to make a play on Markiplier's, "I LOVE SENPAI, YES I DO! HE'S FOR ME, NOT FOR YOU!" at the end, just in case anyone caught that. xDD