Demigods: In Paris (a Miraculous Ladybug and Percy Jackson crossover)

Percy has a friend???

"So you think that Ladybug will go along with the plan?" Adrien asked Plagg, who was pretending to eat his cheese and not stare forlornly out of the window.

"Of course. Y'know, usually the miraculous holder respects their kwami. If Tikki tells Ladybug she can trust you, she will."

"Okay," Adrien sighed. Plagg continued staring out the window.

"What's out there that's so interesting?" Adrien asked eventually, sitting up to peer out.

"Huh?" Plagg's attention snapped back to the camembert. "Oh, nothing."

"It's not nothing. You've been staring since Ladybug's kwami came to visit."

"If you really want to know, nosy, I thought I sensed something whilst Tikki was here."

"What? Is it still there?"

"Something old and powerful... But not as much as me, obviously. Something that I didn't think existed anymore, but hey. The aura has reduced, but I can still feel it if I try."

"Do you know what it was?"

"Full of questions today, huh? It felt like... but no, it couldn't be."

"Couldn't be what? Plagg, what did it feel like?"

"Nothing, okay! Now shut up and let me eat my cheese."

Adrien sighed, and resumed looking out the window. He noticed a red figure running across the rooftops just before the sounds of screaming filled his ears.

"Plagg, claws out!" He shouted, and transformed into Chat Noir.

Ladybug was already mid-fight by the time he reached the scene. He perched on a rooftop for a moment, surveying the akuma. It looked like some kind of huge snake monster with nine heads, and Chat Noir couldn't see any obvious place where the akuma could be. As he watched, it spat some kind of liquid at Ladybug, who narrowly avoided it. The road hissed where the liquid landed - some kind of acid? Razor-sharp teeth snapped dangerously close to his partner, so he swung into the fray, shouting a quick hello to Ladybug.

"About time!" She yelled back. "I can't get close enough to figure out where the akuma is!"

"I can't see anything either," Chat called.

"No! Bad snake! Get back here!" Ladybug cried as the monster turned away and began biting at civilians. "It doesn't seem to be interested in us," she explained to Chat Noir. "Usually they come after the miraculouses, but this one just seems intent on terrorising people!"

She threw her yo-yo at on of the snake's heads. It wrapped around it, yanking it away from the civilians and causing it to hiss in what could have been pain or frustration.

"Forget what I said about the yo-yo," Chat heard someone say from below. "That was pretty neat."

The superhero looked over the perch he was sat on to see two teenagers running below him, going towards the monster, instead of away. "Hey!" He called. "You two, you need to get out of here! That thing is dangerous!"

"We know!" The boy called back cheerfully. He seemed familiar... Had Adrien seen him talking to Marinette and Alya earlier?

"Bunch of crazies," Chat Noir muttered, leaping down into the street in front of them and balancing his baton across his shoulders. "Look, you can't come this way. People are getting hurt, and I need to do my job, not look after you."

"People are getting hurt, and you need our help," the blonde girl said. "Don't believe us?"

"No!" Chat Noir insisted. "Look, I'm here to protect citizens. You may be new to Paris, but that doesn't mean you can get in my way. Leave."

The girl leaned in close. "Let us past, Adrien."

Chat Noir leapt back in shock. "What? How do you know-" But the teenagers were already running at the akuma. "Stop!" He yelled, but it was too late.

"Hey Snake head!" The crazy boy yelled. "Looking for me?"

Chat Noir was expecting the monster to ignore him like it had Ladybug and him, but instead the monster whipped around, tail slamming into a building, and roared.

"That's right!" The boy called in challenge. "It's me, your old pal!"

The boy... knew the akumatised person?

Ladybug noticed what was gong on and ran over. "Percy?!" She yelled. "What are you doing here?!"

"No time to explain," Percy yelled back. "But this isn't an akuma!"

"What do you mean? This can't be a real..."

"It's a hydra! And it doesn't like me very much!" Percy dodged a spray of acid and a biting head, and pulled something out of his pocket. The next thing Chat Noir knew, there was a gleaming sword in his hand. The girl had vanished.

"WHAT?! Where did that come from?" Chat yelped. "Do you even know how to use that thing?"

In reply, the boy dodged another biting set of teeth and launched himself at the beast's torso, slashing at it with the sword. Instead of blood, golden dust leaked out of the cuts. Chat's eyes were wide.

"Cat got your tongue?" Chat jumped almost out of his skin as he noticed Ladybug beside him.

"Milady!" He gasped. "What's going on? Are we just supposed to let that boy kill it? He knew my-"

"Identity? Yeah, the pair of them found me at my house earlier. Apparently they followed my kwami after they saw it leave your house."

"My house? You mean-"

"They wouldn't tell me who you were," Ladybug pulled a face. "Said it was really obvious now that they knew both of us."

"Huh. Speaking of, what did your kwami spy tell you? Are you going to trust me?"

"Despite my instincts, yes. I'll write you a note, although I'm still curious to how you're going to get it into the manor. "

Chat didn't bother to respond, too busy staring at her bluebell eyes as he remembered what the kwamis had told him.

"Listen, bugaboo. Earlier, your kwami told me something- about soulmates."

"If this is your attempt at convincing me we're supposed to be together, I'm not interested. My heart belongs to someone else." Adrien. Her heart belongs to... me? But she'll never know unless I tell her. "Besides, we can't just stand here and let Percy and Annabeth fight that thing by themselves. We need to go help!"