Here's a full story for your idea!

*Blood Moon Over St. Louis*

The streets of St. Louis were quiet at night, but Dean Winchester knew better than to trust silence. It was the kind of quiet that meant something was lurking in the shadows, waiting. Sam walked beside him, eyes scanning the dimly lit alleys.

"Vampires have been hitting the outskirts," Sam said, reading over his phone. "Bodies drained, same M.O. as the nest we took out in Omaha."

Dean sighed. "Great. Another bloodsucker infestation."

They turned a corner, heading toward a boarded-up convenience store—one of the last known places a victim was seen. But before they could reach the door, a figure stepped out from the alley.

A teenager, no older than sixteen, with shaggy blue-streaked hair and a leather jacket. They held a machete, the blade reflecting the streetlight. Their stance was firm, confident, like they knew exactly what they were doing.

"Stay back," the teen warned. "Vamps are nesting here."

Dean and Sam exchanged a glance.

"And you are…?" Dean asked, raising an eyebrow.

"Blu," the teen said. "And you're in my hunt."

Sam huffed a small laugh. "Your hunt?"

Blu's grip on the machete tightened. "Yeah. Been tracking these leeches for weeks. And you're about to mess it up."

Dean smirked, crossing his arms. "Listen, kid. We've been hunting vamps since before you were born. Maybe let the professionals handle this."

Blu rolled their eyes. "I know how to take out a vamp, thanks." They held up a silver flask and shook it. "Dead man's blood. I do my homework."

That caught Sam's interest. "Where'd you learn about that?"

Blu hesitated for a second before muttering, "My brother. He—uh, he used to hunt."

Dean caught the flicker of sadness in their voice. He knew that tone too well.

Before he could say anything, a noise echoed from inside the convenience store—something shuffling. The three of them tensed.

"Guess we're doing this together," Dean said, pulling out his machete.

Blu nodded, their expression shifting to pure focus.

The three of them crept into the store, moving past overturned shelves and broken glass. The air smelled of mildew and something metallic—blood.

Then, from the darkness, glowing red eyes flickered.

The first vampire lunged, fangs bared. Blu moved fast, sidestepping and slicing their machete across its chest. It howled, stumbling back.

Another vamp came from the side, aiming for Sam, but Dean intercepted with a brutal swing, decapitating it instantly.

Blu ducked under a clawed hand, jabbing a syringe of dead man's blood into a third vamp's neck. It staggered, hissing, and Blu swung their machete, taking its head clean off.

"Nice move," Dean said, impressed.

"Thanks," Blu panted.

Within minutes, the nest was reduced to corpses. Sam wiped his blade on his sleeve, nodding in approval.

"Alright, kid," Dean said. "I'll admit it. You can handle yourself."

Blu grinned. "Told you."

Sam studied them. "So, what's next for you?"

Blu's smile faded. "I keep hunting. It's what I do." They sheathed their machete. "You two should get out of here before the cops show up. They tend to notice when heads start rolling."

Dean smirked. "Right. And what about you?"

Blu shrugged. "I know how to disappear."

Something about the kid reminded Dean of himself at that age—young, angry, and carrying too much weight.

He reached into his pocket, pulling out a slip of paper. "Here. My number. In case you run into something bigger than you can handle."

Blu took it, looking at him like they weren't sure if this was a test. Then they smirked. "Thanks, old man."

Dean scowled. "Old man?"

But Blu was already walking away, disappearing into the night.

Sam chuckled. "You kinda walked into that one."

Dean groaned. "Whatever. Let's go."

As they left the ruined store, Dean had a feeling that wasn't the last time they'd see Blu.

Not by a long shot.

What do you think? Want any tweaks?